#!/usr/bin/env python3
"""
SRC - simple revision control.

Things to know before hacking this:

All the code outside the RCS and SCCS classes (and the RevisionMixin
helper) is intended to be generic to any file-oriented VCS.

SRC and RCS/SCCS have different goals in managing locks.  RCS/SCCS
wants to keep the workfile read-only except when it's explicitly
checked out, SRC wants to leave it writeable all the time.  Thus,
the checkin sequence is "release lock; check in; assert lock".  If
this seems confusing, it's because in RCS/SCCS terminology, locked is
writeable and unlocked is read-only.

Despite appearances, this code does not actually use RCS locks (and
sets locking to non-strict).  That just happens to be a handy way to
record which revision the user last checked out, which is significant
for future checkouts and for branching.

With sufficient cleverness it would be possible to go in a different
direction - leave the master unlocked at all times except during the
commit sequence, intervening with a chmod to turn off write
protection on the workfile when RCS/SCCS would normally turn it on.
I had this as a to-do for a long time but have abandoned the
concept; fighting RCS/SCCS's notion of when the workfile ought to be
write-locked seems too likely to lead to weird bugs in unexpected
situations.

In an ideal world, we'd get rid of A status. The SCCS back end doesn't
have it, because the only way to register new content is by "sccs add"
on an already existing file and that creates a new SCCS master with
the content checked in as the first commit.  RCS ci works that way as
well.  On the other hand, if you use rcs -i foo it creates a master foo,v
but does *not* stuff it with the content of any corresponding foo.  This
is what A status means.

Top of the list of things that people will bikeshed about is the
letter codes returned by 'src status'.  Different VCSes have
conflicting ideas about this.  The universal ones are 'A' = Added,
'M' = Modified, and '?' = Untracked.  Here's a table of the ones
in dispute.  Entries with '-' mean the VCS does not have a closely
corresponding status.

                  git     hg     svn      src
Unmodified        ' '     '='    ' '      '='
Renamed           'R'      -      -        -
Deleted           'D'     'R'    'D'       -
Copied            'C'      -      -        -
Ignored           '!'     'I'    'I'      'I'
Updated/unmerged  'U'      -      -        -
Missing            -      '!'    '!'      '!'
Locked             -       -     'L'      'L'

(hg used to use 'C' as the code for unmodified status.)

This is a bit oversimplified; it is meant not as a technical
comparison but rather to illustrate how bad the letter collisions are.
SRC follows the majority except for absolutely *not* using a space as
a status code; this makes the reports too hard to machine-parse.

"""
# SPDX-FileCopyrightText: Copyright Eric S. Raymond <esr@thyrsus.com>
# SPDX-License-Identifier: BSD-2-Clause

from __future__ import annotations

# This code requires Python 3.

# pylint: disable=fixme,line-too-long,too-many-lines,invalid-name,no-value-for-parameter,no-else-break,no-else-return,no-else-continue,missing-function-docstring,comparison-with-callable,consider-using-f-string,too-many-public-methods,too-many-nested-blocks,consider-using-with,too-many-locals,too-many-branches,unnecessary-lambda-assignment

# pylint: disable=multiple-imports
import sys, os, subprocess, time, calendar, stat, glob
import shutil, difflib, io, re, signal
import tempfile, email.utils
import struct, fcntl, termios, errno, inspect, pydoc
import html, shlex
from collections.abc import Callable, Iterable, Sequence
from types import FrameType, TracebackType
from typing import Any, BinaryIO, NoReturn, TextIO

try:
    import curses
except ImportError:  # pragma: no cover
    pass

version: str = "1.45"

# General notes on binary/text handling:
#
# * Use binary I/O to read/write data from/to files and subprocesses;
#   where the exact bytes are important (such as in checking for
#   modified files), use the binary data directly.
#
# * Use latin-1 encoding to transform binary data to/from Unicode when
#   necessary; this ensures that bytes 0x80..0xff are passed through and
#   not clobbered.  The polystr and polybytes functions are used to make
#   this transformation explicit.
#
# * Construct custom stdin, stdout, and stderr streams that force the
#   same encoding. Without this change, 0x80..0xff written to stdout
#   will be garbled in unpredictable ways.

master_encoding: str = "latin-1"


def htmlescape(s: str) -> str:
    return html.escape(s).replace("&#x27;", "'")


def polystr(obj: object) -> str:
    "String factory function"
    if isinstance(obj, str):
        return obj
    if not isinstance(obj, bytes):
        return str(obj)  # pragma: no cover (interactive only)
    return str(obj, encoding=master_encoding)


def polybytes(s: str | bytes) -> bytes:
    "String encoding function"
    if isinstance(s, bytes):
        return s
    return bytes(s, encoding=master_encoding)


def polystream(stream: Any) -> io.TextIOWrapper:
    "Standard input/output wrapper factory function"
    return io.TextIOWrapper(stream.buffer, encoding=master_encoding, newline="\n")


def polyutf8str(obj: object) -> str:
    "String factory function, utf-8 variant"
    if isinstance(obj, str):
        return obj
    if not isinstance(obj, bytes):
        return str(obj)  # pragma: no cover (interactive only)
    return str(obj, encoding="utf-8")


def polyutf8bytes(s: str | bytes) -> bytes:
    "String encoding function, utf-8 variant"
    if isinstance(s, bytes):
        return s
    return bytes(s, encoding="utf-8")


sys.stdin = polystream(sys.stdin)
sys.stdout = polystream(sys.stdout)
sys.stderr = polystream(sys.stderr)

# Note: Avoid using unbolded blue (poor luminance contrast with black
# terminal-emulator background) or bolded yellow (poor contrast with
# white background.)
RESET = BOLD = ""
CBLACK = CBLUE = CGREEN = CCYAN = CRED = CMAGENTA = CYELLOW = CWHITE = ""


def init_colors() -> None:  # pragma: no cover
    curses.setupterm()
    # pylint: disable=global-statement
    global RESET, BOLD
    RESET = curses.tigetstr("sgr0")
    if RESET is not None:
        RESET = polystr(RESET)
    else:
        RESET = ""
    BOLD = curses.tigetstr("bold")
    if BOLD is not None:
        BOLD = polystr(BOLD)
    else:
        BOLD = ""
    colors = {
        "setaf": [0, 4, 2, 6, 1, 5, 3, 7],  # ANSI colors
        "setf": [0, 1, 2, 3, 4, 5, 6, 7],
    }  # legacy colors
    for k, v in colors.items():
        x = curses.tigetstr(k)
        if x:
            for i, c in enumerate(
                ["black", "blue", "green", "cyan", "red", "magenta", "yellow", "white"]
            ):
                cap = curses.tparm(x, v[i])
                if cap is not None:
                    cap = polystr(cap)
                else:
                    cap = ""
                globals()["C" + c.upper()] = cap
            break


if "curses" in sys.modules and sys.stdout.isatty():  # pragma: no cover
    try:
        init_colors()
    except (curses.error, AttributeError):
        pass


def rfc3339(t: float) -> str:
    "RFC3339 string from Unix time."
    return time.strftime("%Y-%m-%dT%H:%M:%SZ", time.gmtime(t))


def announce(msg: str) -> None:
    sys.stdout.write("src: " + msg + "\n")


def croak(msg: str) -> NoReturn:
    sys.stdout.flush()
    sys.stderr.write("src: " + msg + "\n")
    raise SystemExit(1)


def tabular_escape(text: object) -> str:
    "Escape text so it can be embedded safely in a tab-separated record."
    text = str(text)
    text = text.replace("\\", "\\\\")
    text = text.replace("\t", "\\t")
    text = text.replace("\n", "\\n")
    text = text.replace("\r", "\\r")
    return text


def emit_tabular(fields: Iterable[object]) -> None:
    "Emit a tab-separated record."
    sys.stdout.write("\t".join(tabular_escape(field) for field in fields) + "\n")


debug: int = 0
DEBUG_COMMANDS: int = 1  # Show commands as they are executed
DEBUG_TREESTATE: int = 2  # Dump directory state
DEBUG_SEQUENCE: int = 3  # Sequence debugging
DEBUG_PARSE: int = 4  # Debug logfile parse

quiet: bool = False  # option -q: run more quietly
pseudotime: bool = False  # option -T: artificial clock for regression testing
forced_repodir: bool = False  # option -S: user selected a repository directory

backend: Any
repodir: str
multidir: bool
startdir: str


def textopen(filename: str, mode: str) -> TextIO:
    "Open a text file with SRC's master encoding."
    return io.open(filename, mode, encoding=master_encoding)


logstream: TextIO = sys.stderr


def logit(msg: str) -> None:
    logstream.write(msg)


class popen_or_die:
    "Read or write from a subordinate process."

    def __init__(self, command: str, legend: str | None = "", mode: str = "r") -> None:
        self.command = command
        self.legend = legend
        self.mode = mode
        # Pipe to the correct streams depending on the chosen mode
        self.stdin = subprocess.PIPE if mode == "w" else None
        self.stdout = subprocess.PIPE if mode == "r" else None
        self.stderr = subprocess.STDOUT if mode == "r" else None
        if self.legend:
            self.legend = " " + self.legend
        self.fp: Any = None

    def __enter__(self) -> BinaryIO:
        if debug >= DEBUG_COMMANDS:
            if self.mode == "r":
                logit(
                    "%s: reading from '%s'%s\n"
                    % (rfc3339(time.time()), self.command, self.legend)
                )
            else:
                logit(
                    "%s: writing to '%s'%s\n"
                    % (rfc3339(time.time()), self.command, self.legend)
                )
        try:
            # The I/O streams for the subprocess are always bytes; this
            # is what we want for some operations, but we will need
            # to decode to Unicode for others to work in Python 3, as
            # explained in the general notes.
            self.fp = subprocess.Popen(
                self.command,
                shell=True,
                stdin=self.stdin,
                stdout=self.stdout,
                stderr=self.stderr,
            )
            # The Python documentation recommends using communicate() to
            # avoid deadlocks, but this doesn't allow fine control over
            # reading the data; since we are not trying to both read
            # from and write to the same process, this should be OK.
            return self.fp.stdout if self.mode == "r" else self.fp.stdin
        except (OSError, IOError) as oe:  # pragma: no cover
            croak("execution of %s%s failed: %s" % (self.command, self.legend, oe))
        return None  # pragma: no cover

    def __exit__(
        self,
        extype: type[BaseException] | None,
        value: BaseException | None,
        traceback_unused: TracebackType | None,
    ) -> bool:
        if extype:  # pragma: no cover
            if debug > 0:
                raise extype(value)
            croak("fatal exception in popen_or_die.")
        if self.fp.stdout is not None:
            # This avoids a deadlock in wait() below if the OS pipe
            # buffer was filled because we didn't read all of the data
            # before exiting the context manager (shouldn't happen but
            # this makes sure).
            self.fp.stdout.read()
        self.fp.wait()
        if self.fp.returncode != 0:  # pragma: no cover
            croak("%s%s returned error." % (self.command, self.legend))
        return False


def screenwidth() -> int:  # pragma: no cover
    "Return the current width of the terminal window."
    default_width = 73

    if "COLUMNS" in os.environ:
        return int(os.environ["COLUMNS"])

    try:
        return struct.unpack(
            "HHHH", fcntl.ioctl(0, termios.TIOCGWINSZ, struct.pack("HHHH", 0, 0, 0, 0))
        )[1]
    except IOError as e:
        # ENOTTY isnormal for no terminal under Linux, but
        # Mac High Sierra can throw ENODEV.
        if e.errno in (errno.ENOTTY, errno.ENODEV):
            return default_width
        else:
            raise e


WIDTH = screenwidth() - 1


def modified(workfile: str, history: History | None = None) -> bool:
    "Has the workfile been modified since it was checked out?"
    # Alas, we can't rely on modification times; it was tried, and
    # os.utime() is flaky from Python - sometimes has no effect.  Where
    # the bug is - Python, glibc, kernel - is unknown.  Even if we
    # could, it's nice to catch the case where an edit was undone.
    #
    # If no revisions, bail out
    if not backend.has_revisions(workfile):
        return False
    if history is None:
        history = History(workfile)
    with backend.manager(workfile) as xc:
        with backend.cat(xc.pathbase, history.current().native) as bstream:
            base_content = bstream.read()  # this data will be binary
            if os.path.getsize(xc.pathbase) != len(base_content):
                return True
            with open(xc.pathbase, "rb") as fp:
                workfile_content = fp.read()
            # This comparison uses the binary data for maximum accuracy
            return base_content != workfile_content


def relative(d: str | None = None) -> str:
    # Only used for debug/croak output
    return os.path.relpath(os.getcwd() if d is None else d, startdir)


def treedump(legend: str) -> None:
    # Visibly dump the state of the directory we're in
    # Used for debugging instrumentation only.
    logit(legend + "\n")
    logit(polystr(capture_or_die("ls -laR " + startdir)))


def rename(source: str, target: str, legend: str | None) -> None:
    if debug >= DEBUG_COMMANDS:
        logit("rename(%s, %s) %s\n" % (source, target, legend))
    os.rename(source, target)


def chdir(target: str, legend: str | None) -> None:
    if debug >= DEBUG_COMMANDS:
        logit("chdir(%s) %s\n" % (target, legend))
    os.chdir(target)


def caller(uplevel: int, legend: str = "") -> str:
    "Look up the stack for the callers of this function (for diagnostics)"
    if legend:
        legend = " " + legend
    return str(inspect.stack()[1 + uplevel][0].f_code.co_name) + legend


def do_or_die(
    dcmd: str,
    legend: str | None = "",
    mute: bool = True,
    missing: str | None = None,
    fatal: bool = True,
) -> int:
    "Either execute a command or die."
    if legend:
        legend = " " + legend
    if debug == 0 and mute:
        muteme = " >/dev/null 2>&1"
    else:
        muteme = ""
    say = croak if fatal else announce
    dcmd = "(" + dcmd + ")" + muteme
    if debug >= DEBUG_TREESTATE:
        treedump("Before command " + dcmd)
    if debug >= DEBUG_COMMANDS:
        logit("at %s executing '%s'%s\n" % (relative(), dcmd, legend))
    retcode = 0
    try:
        retcode = subprocess.call(dcmd, shell=True)
        if retcode < 0:  # pragma: no cover
            croak("%s was terminated by signal %d." % (repr(dcmd), -retcode))
        elif retcode != 0:  # pragma: no cover
            errmsg = "%s returned %d." % (repr(dcmd), retcode)
            if retcode == 127:
                if missing is None:
                    missing = backend.__class__.__name__
                errmsg += "\nYou probably need to install %s." % missing
            say(errmsg)
    except (OSError, IOError) as e:  # pragma: no cover
        say("execution of %s%s failed: %s" % (repr(dcmd), legend, e))
    if debug >= DEBUG_TREESTATE:
        treedump("After command")
    return retcode


def capture_or_die(command: str) -> bytes:
    "Run a specified command, capturing the output."
    if debug >= DEBUG_COMMANDS:
        logit("%s: capturing %s\n" % (rfc3339(time.time()), command))
    try:
        # This will return binary data
        content = subprocess.check_output(command, shell=True)
    except (subprocess.CalledProcessError, OSError) as oe:  # pragma: no cover
        croak("execution of %s failed: %s" % (repr(command), oe))
    if debug >= DEBUG_COMMANDS:  # pragma: no cover
        logit(polystr(content))
    return content


# pylint: disable=too-many-instance-attributes
class HistoryEntry:
    "Capture the state of a native revision item in the log."

    def __init__(self, history: History) -> None:
        "Initialize a history entry."
        self.history: History = history
        self.revno: int | None = None
        self.native: str | None = None  # magic cookie only interpreted by back end
        self.headers: dict[str, Any] | None = None
        self.log: str = ""
        self.date: str | None = None
        self.parent: HistoryEntry | None = None
        self.child: HistoryEntry | None = None
        self.branch: str | None = None

    def selected(self) -> bool:
        "Is this the currently selected revision in the history list?"
        return self == self.history.current()

    def getdate(self, who: str) -> str | None:
        "Get the revision's commit date."
        if self.headers and not pseudotime:
            return self.headers.get(who + "-date") or self.date
        return self.date

    def unixtime(self, who: str) -> tuple[int, int]:
        "Get the Unix timestamp of this revision."
        date = self.getdate(who)
        try:
            t = calendar.timegm(time.strptime(date, "%Y-%m-%dT%H:%M:%SZ"))
            offset = 0
            if self.headers and not pseudotime:
                offset = self.headers.get(who + "-date-offset") or 0
            return t, offset
        except (TypeError, ValueError):  # pragma: no cover
            croak("garbled date %s" % date)
        return None  # pragma: no cover

    def __str__(self) -> str:
        return "<%s = %s>" % (self.revno, self.native)


def registered(workfile: str) -> bool:
    "Is this a workfile for a registered history?"
    return os.path.exists(backend.history(workfile))


# pylint: disable=too-many-instance-attributes
class History:
    "Encapsulate a revision list and some methods on it"

    def __init__(self, filename: str) -> None:
        "Intialize a history list."
        self.filename: str = filename
        self.revlist: list[HistoryEntry] = []
        self.symbols: dict[str, str] = {}
        self.tipbranch: str = "trunk"
        self.lockrevs: list[str] = []
        self.description: str = ""  # Not currently used
        if not registered(self.filename):
            croak("%s is not registered" % self.filename)
        self.by_revno_d: dict[int, HistoryEntry] = {}
        self.by_native_d: dict[str, HistoryEntry] = {}
        if debug >= DEBUG_COMMANDS:
            logit("parsing %s\n" % self.filename)
        try:
            d = os.path.dirname(filename)
            if d:
                chdir(d, "before getting history")
            backend.parse(self, os.path.basename(filename))
        finally:
            chdir(startdir, "after getting history")
        self.lift_headers()
        self.normalize_header_dates()

    def build_indices(self) -> None:
        for item in self.revlist:
            self.by_revno_d[item.revno] = item
            self.by_native_d[item.native] = item
        for item in self.revlist:
            item.parent = self.by_native_d.get(backend.pred(item.native))
            item.child = self.by_native_d.get(backend.succ(item.native))
        if debug >= DEBUG_PARSE:
            logit("Symbols: %s\n" % self.symbols)
            for item in self.revlist:
                logit("Item %s\n" % item)
            logit("By revision: %s\n" % self.by_revno_d.keys())
        if self.revlist:
            for name, rev in list(self.symbols.items()):
                if backend.isbranch(rev):
                    base = backend.branch_to_base(rev)
                    tip = backend.branch_to_tip(rev, self)
                    while True:
                        if base in self.by_native_d:
                            current = self.by_native_d[base].branch
                            if current is None or name == self.tipbranch:
                                self.by_native_d[base].branch = name
                        if base == tip:
                            break
                        base = backend.succ(base)

    def lift_headers(self) -> None:
        valid = (
            "author",
            "author-date",
            "committer",
            "committer-date",
            "mark",
            "parents",
        )
        for item in self.revlist:
            headers = {}
            i = 0
            while True:
                n = item.log.find("\n", i)
                if n < 0:
                    break
                header = item.log[i:n].split(":", 1)
                if len(header) != 2:
                    break
                key = header[0].lower()
                if key in valid:
                    headers[key] = header[1].strip()
                    i = n + 1
                else:
                    break
            # eat blank line between headers and body
            while i < len(item.log) and item.log[i] == "\n":
                i += 1
            item.log = item.log[i:]
            if headers:
                item.headers = headers

    def normalize_header_dates(self) -> None:
        for item in self.revlist:
            if item.headers:
                for k in tuple(item.headers):
                    if k.endswith("-date"):
                        d = email.utils.parsedate_tz(item.headers[k])
                        if d:
                            u = email.utils.mktime_tz(d)
                            item.headers[k] = rfc3339(u)
                            item.headers[k + "-offset"] = d[9] if d[9] else 0

    def __len__(self) -> int:
        return len(self.revlist)

    def current(self) -> HistoryEntry | None:
        "Return the revision currently checked out."
        # Yes, this looks weird.  The idea is: Try to return the locked
        # revision.  If that blows up, try to return the tip revision of
        # the current branch.  If that blows up, return None.
        try:
            return self.by_native_d[self.lockrevs[0]]
        except (IndexError, KeyError):
            try:
                return self.by_native_d[
                    backend.branch_to_tip(self.symbols[self.tipbranch], self)
                ]
            except (IndexError, KeyError):  # pragma: no cover
                return None

    def current_branch_revisions(self, backwards: bool = False) -> list[HistoryEntry]:
        "Return a list of items that are descendants or ancestors of current."
        if debug >= DEBUG_SEQUENCE:
            logit(("current_branch_revisions(%s)\n" % self.current()))
        selection = []
        p = self.current()
        if p is not None:
            selection = [p]
            while True:
                if p.parent is None:
                    break
                else:
                    p = p.parent
                selection = [p] + selection
            s = self.current()
            while True:
                s = s.child
                if s is None:
                    break
                selection.append(s)
            if backwards:
                selection.reverse()
        return selection

    def tip(self, rev: str | None = None) -> HistoryEntry:
        "Return the tip revision of the branch of the given native revision."
        if rev is None:
            rev = self.current().native
        s = self.by_native_d[rev]
        while True:
            if s.child is None:
                return s
            else:
                s = s.child

    def native_to_revno(self, revision: str) -> int | None:
        "Map a native ID to a revno"
        item = self.by_native_d.get(revision)
        return item and item.revno

    def by_revno(self, revno: int) -> HistoryEntry:
        "Map a revno to a revision item."
        try:
            return self.by_revno_d[revno]
        except KeyError:  # pragma: no cover
            if revno == 0:
                # This case comes up if we try to select the tip
                # revision of a history without revisions.
                croak("{0} has no revisions".format(self.filename))
            else:
                croak("{0} has no revno {1}".format(self.filename, revno))
        return None  # pragma: no cover

    def revno_to_native(self, revno: int) -> str:
        "Map a revno to a native ID"
        return self.by_revno(revno).native

    def reportme(self) -> str:
        "Report the current file's name, with branch label if it's not trunk."
        branch_part = "" if self.tipbranch == "trunk" else "(" + self.tipbranch + ")"
        return branch_part + self.filename


help_topics: dict[str, str] = {
    "topics": """
The following help topics are available:

intro       -- Basic concepts: commits, tags, branches. The form of commands.
revisions   -- How to specify ranges of commits to operate on.
commands    -- a summary of the commands.
init        -- the initialize command, which does nothing
commit      -- the commit command: how to commit changes to a file.
amend       -- the amend command: editing stored change comments.
uncommit    -- the uncommit command: remove the last commit.
checkout    -- the checkout command: retrieving historical versions of files.
cat         -- the cat command: dumping revisions to standard output.
status      -- the status command: more details and unusual status codes.
log         -- the log command: dump commit log information to standard output.
list        -- the list command: dump commit summaries to standard output.
diff        -- the diff command: dump revision differences to standard output.
fast-export -- the fast-export command: export history to other systems.
fast-import -- the fast-import command: import history from other systems.
srcify      -- the srcify command: change management from SCCS/RCS to src.
ignores     -- .srcignore files and their uses.

The 'help', 'rename', 'ls', 'move', 'copy', 'visualize', and 'version'
commands are completely described in the command summary.
""",
    "intro": """
SRC Introduction

    SRC (or src) is designed for version control on single-file
    projects. To start a single-file project, just create a file
    and commit it; this will create a subdirectory called .src
    if one does not already exist, and put your file history there.

    A SRC history is a sequence of commits numbered in strict time order
    starting from 1.  Each holds a modification to the file, a comment,
    and the date-time of the commit.

    The sequence also has a branch structure.  By default there is
    just one branch named 'trunk'.  You can start a new named branch
    at any commit.  Branches can later be renamed or deleted.  Because
    of branching, parent and child commits do not necessarily have
    consecutive numbers.

    Commits will always be added to the tip of the current branch.
    You can change the current branch by either checking out a revision
    that is on that branch, or using a 'src branch' command to
    explicitly change the current branch.

    You can assign tags (names) to point to commits.  They too can be
    renamed later or deleted.

    The general form of a SRC command is

        src verb [switches] [revision-spec] [files...]

    That is, a command verb is followed by optional switches, which are
    (sometimes) optionally followed by a range of commits to operate
    on, which is optionally followed by a list of files to operate on.
    Usually you will specify either a revision range or multiple files,
    but not both.

    The token '--' tells the command-line interpreter that subcommands,
    switches, and revision-specs are done - everything after it is a
    filename, even if it looks like a subcommand or revision number.

    A filename can be a path. In that case SRC will behave as though
    it were running in the lowest-level directory on the path and called
    with the path basename.

    If you do not specify any files, SRC will operate sequentially on
    each individual file in the current directory with a history.

    A good help topic to read after this one would be 'revisions'.
""",
    "revisions": """
SRC Revisions

    A 'revision' is a 1-origin integer, or a tag name designating an
    integer revision, or a branch name designating the tip revision of
    its branch, or '@' meaning the currently fetched revision.  Revision
    numbers always increase in commit-date order.

    A revision range is a single revision, or a pair of revisions 'M-N'
    (all revisions numerically from M to N) or 'M..N' (all revisions
    that are branch ancestors of N and branch successors of M).  If N is
    less than M, the range is generated as if N >= M then reversed.

    If SRC complains that your revision spec looks like a nonexistent
    filename, you can prefix it with '@' (this is always allowed).

    Some commands (help, commit, status, delete/rename commands for tags
    and branches, uncommit, ls, move, copy, fast-import, release, srcify,
    version) don't take a revision spec at all and will abort if you give one.

    Some commands (amend, checkout, cat, tag and branch creation)
    optionally take a singleton revision spec.

    Some commands (log, list, diff, fast-export) accept a range or a
    singleton.

    Unless otherwise noted under individual commands, the default
    revision is the tip revision on the current branch.

    A good topic to read next would be 'commands'.
""",
    "commands": """
SRC Commands Summary

src help [command]
    Displays help for commands.

src init
    This command is unnecessary and does nothing. It is provided
    to reduce surprise for people who don't expect the first 
    commit into a file in a new directory to initialize a 
    repository there.

src commit [-|-m 'string'|-f 'file'|-e|-b branch] ['file'...]
    Enters a commit for specified files, separately to each one.
    A history is created for the file if it does not already exist.
    With '-', take comment text from stdin; with '-m' use the following
    string as the comment; with '-f' take from a file.  With '-e', edit
    even after '-', '-f' or '-m'. 'ci' is a synonym for 'commit'.  The -b
    option attaches the commit to the named branch, making it the default
    for future commits.

src amend [-|-m 'string'|-f 'file'|-e] ['revision'] ['file'...]
    Amends the stored comment for a specified revision, defaulting to
    the latest revision on the current branch.  Flags are as for commit.

src uncommit ['file'...]
    Removes the latest revision on the current branch, leaving the workfile
    unaltered.

src checkout ['revision'] ['file'...]
    Refresh the working copies of the file(s) from their history files.
    Sets the default branch for future checkins to that of whatever revision 
    you check out. 'co' is a synonym for 'checkout'.

src cat ['revision'] ['file'...]
    Send the specified revisions of the files to standard output.

src status [-a] [-q] ['file'...]
    '=' = unmodified,   'M' = modified, '!' = missing,
    '?' = not tracked,  'I' = ignored,  'A' = added,
    'L' = locked (recover with 'src checkout').
    Find more details under 'help status'. 'st' is a synonym for
    'status'.

src tag [list|-l|create|-c|delete|del|-d] ['name'] ['revision'] ['file'...]
    List tags, create tags, or delete tags.  Create/delete takes a
    singleton revision, defaulting to the current branch tip.  List
    defaults to all revisions.

src branch [list|-l|create|-c|delete|del|-d] ['name'] ['file'...]
    List, create, or delete branches.  When listing, the active branch
    is first in the list.  The default branch is 'trunk'.  Create/delete
    takes a singleton revision, defaulting to the current branch tip; on
    create that branch becomes the default for future commits. List defaults
    to all revisions, including 0 (the trunk root phantom revision).

src rename ['tag'|'branch'] ['oldname'] ['newname']  ['file'...]
    Rename a tag or branch.  Refuses to step on an existing symbol or
    rename a nonexistent one. 'rn' is a synonym for 'rename'.

src list [(-<n>|-l <n>)] [-P] [-f 'fmt'] ['revision-range'] ['file'...]
    Sends summary information about the specified commits to standard
    output.  The summary line tagged with '*' is the state that the file
    would return to on checkout without a revision-spec.  See 'help
    list' for information about custom formats.  Use '-<n>' or '-l <n>',
    where <n> is a number, to limit the listing length.  The '-P'
    option emits porcelain output with one tab-separated record per
    revision and no decorative headers. Default range is the current
    branch, reversed.

src log [-v] [(-<n>|-l <n>)] [-P] [((--patch|-u|-c) [-b|-w])] ['revision-range'] ['file'...]
    Sends log information about the specified commits to standard
    output.  Use '-<n>' or '-l <n>', where <n> is a number, to limit the
    listing length.  Default range is the current branch, reversed.
    Use '-P' for porcelain output with one tab-separated record per
    revision and no decorative headers or color. Use '--patch' or '-u'
    to also send a unified format diff listing to standard output for each
    revision against its immediate ancestor revision; '-c' emits a context
    diff instead. When generating a diff, '-b' ignores changes in the amount
    of whitespace, and '-w' ignores all whitespace.  Histories imported via
    'fast-import' (when not using its '-p' option) have RFC-822-style headers
    inserted into the log comment to preserve metadata not otherwise representable
    in SRC, such as distinct author and committer identifications and
    dates.  These headers are normally suppressed by 'log', however,
    '-v' shows a summarized view of important headers; '-v -v' shows
    all headers as-is.

src diff [(-u|-c) [-b|-w]] ['revision-range'] ['file'...]
    Sends a diff listing to standard output.  With no revision spec,
    diffs the working copy against the last version checked in.  With
    one revno, diffs the working copy against that stored revision; with
    a range, diff between the beginning and end of the range. 'di' is a
    synonym for 'diff'.

src ls
    List all registered files.

src visualize
    Emit a DOT visualization of repository structures.  To use this,
    install the graphviz package and pipe the output to something like
    'dot -Tpng | display -'. 'vis' is a synonym for 'visualize'.

src move 'old' 'new'
    Rename a workfile and its history.  Refuses to step on existing
    workfiles or histories. 'mv' is a synonym for 'move'.

src copy 'old' 'new'
    Copy a workfile and its history.  Refuses to step on existing files
    or histories. 'cp' is a synonym for 'copy'.

src fast-export ['revision-range'] ['file'...]
    Export one or more projects to standard output as a Git fast-import
    stream.  For a history originally imported from elsewhere, author
    and committer identification is gleaned from the RFC-822-style
    headers inserted into the commit comment by 'fast-import' (if its
    '-p' option was not used).  Otherwise, this information is copied
    from your Git configuration.  The default range is all commits.

src fast-import [-p] ['file'...]
    Parse a git-fast-import stream from standard input.  The
    modifications for each individual file become separate SRC
    histories.  Mark, committer and author data, and mark cross-
    references to parent commits, are preserved in RFC-822-style headers
    on log comments unless the '-p' (plain) option is given, in which
    case this metadata is discarded.  Give arguments to restrict the
    files imported.

src release ['file'...]
    Release locks on files.  This is never necessary in a normal
    workflow, which will be repeated edit-commit cycles, but it may be
    handy if you have to interoperate with other tools that expect RCS
    masters to be in their normal (unlocked/unwriteable) state.

src srcify
    Move a directory from being RCS- or SCCS-managed to being SRC-managed.
    That is: if the current directory contains an RCS directory, rename it
    to .src (but leave any SCCS directory in place).  Then check out all
    masters for editing that are not already checked out.

src version
    Report the versions of SRC, the underlying Python, and the back end.

The omission of 'src remove' is a deliberate speed bump.
""",
    "status": """
src status [-a] [-q] ['file'...]

    The status command shows you the version-control status of files.
    It is designed to be useful for both humans and software front ends
    such as Emacs VC mode.

    The status codes, in roughly most common to rarest, are:

    = - Unmodified.  File is the same as the latest stored revision.
    M - Modified.  File has been changed since the latest stored revision.
    ? - Not tracked.  SRC does not keep a history for this file.
    I - ignored.  This file matches the patterns in '.srcignore'.
    ! - Missing.  There is a history for this file but the workfile is missing.
    A - The file has been registered into SRC but has no commits.
    L - The file is locked/writable.

    Modification status is by content rather than the filesystem's
    last-modified date.  Thus, if you make changes to a work file in
    your editor, then undo them, the file's status returns to '='.

    You can usually recover a file from 'A', 'L', and '!' status with
    'src checkout'.  'A' and 'L' statuses should only occur if you have
    used RCS directly on a file, or if you have called 'src commit' with
    the deliberately undocumented '-a' option meant for Emacs VC's use.

    If you give 'src status' no filename arguments, it surveys all files
    in the current directory but untracked and ignored files are not
    listed.  If you give it filename arguments, status is listed for all
    of them.

    The '-a' option forces status listing of all files.  This differs
    from 'src status *' because the latter will not see dotfiles and
    thus not list the status of them.  The -q option suppresses listing
    of untracked files.
""",
    "init": """
src init

    This command is unnecessary and does nothing. It is provided by
    analogy with the init commands in cvs, git, hg and bzr/brz, as a
    placeholder in scripting and to reduce surprise for people who
    don't expect the first commit into a file in a new directory to
    initialize a repository there.
""",
    "commit": """
src commit [-|-m 'string'|-f 'file'| -e] [-b branch] ['file'...]

    The commit command is how you add revisions to your file history.
    It always adds the contents of the workfile as a revision to the tip
    of the current branch. The -b option puts the commit on a new branch.

    You also use commit on files that have not been registered to start
    an SRC history for them.

    When you commit, you must specify a change comment to go with the
    revision.  There are several ways to do this.

    The '-m' option to the command takes the following string argument
    as the comment.  The '-' option takes the comment text from standard
    input.  The '-f' option takes the comment from a named file.

    If you use none of these, or if you use one of them and the '-e'
    option, SRC will start an editor in which you can compose the
    comment.  Text specified via '-m', '-f', or '-' becomes the initial
    contents of the comment.

    SRC respects the EDITOR variable and calls it on a temporary file to
    create your comment.  The file will have a footer including its name
    and revision which will be discarded when you finish editing.

    If you leave the comment empty (except for the generated footer)
    or consisting only of whitespace, the commit will be aborted.  The
    commit will also be aborted if your editor returns a failure status.

    If you commit to multiple files at once, separate changes will be
    registered for each one, and you may get a separate edit session for
    each (if you have not set the comment text with options, or have
    forced editing with '-e').  This is a major difference from other
    VCSes, which are usually designed to create changesets common to
    multiple files.

    'ci' is a synonym for 'commit'.
""",
    "amend": """
src amend [-|-m 'string'|-f 'file'| -e] ['revision'] ['file'...]

    Use this command to amend (modify) the change comment in a saved
    revision.  The commit date is not changed.

    Takes a singleton revision number, tag, or branch, defaulting to the
    latest revision on the current branch.

    The edit flags and EDITOR variable are interpreted are as for
    commit.  The only difference is that existing change comment is
    appended to any text you specify with switches as the initial
    comment passed to your editor.

    'am' is a synonym for 'amend'
""",
    "uncommit": """
src uncommit ['file'...]

    Remove the latest revision on the current branch, leaving the workfile
    unaltered.  This is analogous to a soft reset in other systems.

    'un' is a synonym for 'uncommit'.
""",
    "checkout": """
src checkout ['revision'] ['file'...]

    Refresh the working copies of the file(s) from their history files.

    Takes a single revision number, tag, or branch name.  The default if
    you give none is the tip revision of the current branch.

    This command is how you discard the contents of a modified workfile.

    You can also use it to revert the workfile to match a previous
    stored revision.  Doing so may, as a side effect, change your
    current branch.

    'co' is a synonym for 'checkout'.
""",
    "cat": """
src cat ['revision'] ['file'...]

    Send the specified revision of each file to standard output.  This
    is not normally very useful with more than one file argument, but
    SRC does not prevent that.

    Takes a single revision number, tag, or branch name.  The default if
    you give none is the tip revision of the current branch.

    This command is mainly intended for use in scripts.
""",
    "tag": """
src tag [list|-l|create|-c|delete|del|-d] ['name'] ['revision'] ['file'...]

    List tags (with '-l'), create tags (with '-c'), or delete tags (with
    '-d').

    Takes at most a singleton revision; the default is the current
    branch tip.

    Tag creation and deletion require a following name argument.  Tag
    creation will not step on an existing tag name, and a nonexistent
    branch cannot be deleted.
""",
    "branch": """
src branch [list|-l|create|-c|delete|del|-d] ['name'] ['file'...]

    List branches (with '-l'), create branches (with '-c'), or delete
    branches (with '-d').

    In the list produced by '-l', the active branch is first in the list.

    Branch creation and deletion require a following name argument.
    Branch creation will not step on an existing branch name, and a
    nonexistent branch cannot be deleted.
""",
    "log": """
src log [-v] [(-<n>|-l <n>)] [-p] [((-u|-c) [-b|-w])] ['revision-range'] ['file'...]

    Sends log information about the specified commits of each file to
    standard output.  The log information includes the revision number,
    the date, and the log comment.

    With no revision, dumps a log of the entire current branch.

    The '-P' option emits porcelain output with one tab-separated
    record per revision. Embedded tabs, newlines, and backslashes are
    escaped, and decorative headers and color are suppressed.

    The '--patch', '-p', or '-u' option additionally sends a unified-format diff listing
    to standard output for each revision against its immediate ancestor
    revision; '-c' emits a context diff instead. When generating a diff,
    '-b' ignores changes in the amount of whitespace, and '-w' ignores
    all whitespace.

    The '-<n>' or '-l <n>' option, where <n> is a number, can be used to
    limit the listing length.

    Histories imported via 'fast-import' (when not using its '-p' option)
    have RFC-822-style headers inserted into the log comment to preserve
    metadata not otherwise representable in SRC, such as distinct author
    and committer identifications and dates.  These headers are normally
    suppressed by 'log', however, '-v' shows a summarized view of
    important headers; '-v -v' shows all headers as-is.
""",
    "list": """
src list [(-<n>|-l <n>)] [-P] [-f 'fmt'] ['revision-range'] ['file'...]

    Sends summary information about the specified commits of each file
    to standard output.  The summary information includes the revision
    number, the date, and the first line of the log comment.

    This command is provided assuming you will use the good practice of
    beginning each commit with a self-contained summary line.

    With no revision, dumps a log of the entire current branch.

    The '-f' option allows you to set a custom format string.  Available
    substitutions are:

    {0} - the file name
    {1} - the revision number
    {2} - the mark '*' if this is the currently checked out revision, else '-'.
    {3} - the date in RFC3339 format
    {4} - the summary line

    The '-<n>' or '-l <n>' option, where <n> is a number, can be used to
    limit the listing length.

    The '-P' option emits porcelain output with one tab-separated
    record per revision. Embedded tabs, newlines, and backslashes are
    escaped, and decorative headers are suppressed.

    'li' is a synonym for 'list'.
""",
    "diff": """
src diff [(-u|-c) [-b|-w]] ['revision-range'] ['file'...]

    Sends a diff listing to standard output.

    With no revision spec, diffs the working copy against the last
    version checked in.  With one revno, diffs the working copy against
    that stored revision; with a range, diff between the beginning and
    end of the range.

    The actual difference generation is done with diff(1).  The default
    diff format is '-u' (unified), but if you specify a '-c' option
    after the verb a context diff will be emitted. '-b' ignores changes
    in the amount of whitespace, and '-w' ignores all whitespace.

    'di' is a synonym for 'diff'.
""",
    "fast-export": """
src fast-export ['revision-range'] ['file'...]

    Export one or more projects to standard output as a git fast-import
    stream.  This can be consumed by 'git fast-import' to create a Git
    repository containing the project history.

    It is possible (though probably not very useful) to fast-export a
    limited range of commits, producing an incremental dump.  In this
    case branch joins are done with the magic ^0 suffix.

    Fast-exporting multiple files produces a single stream with a joint
    history.

    If there is a .srcignore file, it is renamed to .gitignore in the
    stream.

    For a history originally imported from elsewhere, author and
    committer identification is gleaned from the RFC-822-style headers
    inserted into the commit comment by 'fast-import' (if its '-p'
    option was not used).  Otherwise, this information is copied from
    your Git configuration.

    The default range is all commits.
""",
    "srcify": """
src srcify

    Change the current directory with an RCS or SCCS subdirectory to be
    managed by src instead. Any RCS directory is renamed .src. Then all
    files with histories are checked out for editing.
""",
    "fast-import": """
src fast-import [-p] ['file'...]

    Parse a git-fast-import stream from standard input.  The
    modifications for each individual file become separate SRC
    histories.  Give arguments to restrict the files imported.

    The import is actually done with the rcs-fast-import(1) tool, which
    must be on your $PATH for this command to work.

    Some gitspace metadata cannot be represented in the SRC/RCS
    model of version control.  Mark, committer and author data, and
    mark cross-references to parent commits.  These are preserved in
    RFC-822-style headers on log comments unless the '-p' (plain) option
    is given, in which case this metadata is discarded.
""",
    "ignores": """
Making SRC Ignore Certain Files

    You can have a file named '.srcignore' containing the names of files
    that SRC should ignore, or more commonly patterns describing files
    to ignore.

    When SRC is told to ignore a file, it won't show up in 'src status'
    listings unless the '-a' (all) flag is used or you give it as an
    explicit argument.  It will also be ignored when commands that
    expect a list of registered files see it (which could easily happen
    when you use shell wildcards in SRC commands).

    Other version-control systems have these too.  The classic example
    of how to do this is using the pattern '*.o' to ignore C object
    files.  But if you need to do that, you should probably be using a
    multi-file VCS with changesets, not this one.

    Patterns that might be useful with single-file projects include
    '*~' to ignore editor backup files, or '*.html' if you're writing
    documents that render to HTML but aren't sourced in it.

    The repo subdirectory - normally '.src' - is always ignored, but
    '.srcignore' itself is not automatically ignored.

    SRC's pattern syntax is that of Unix glob(3), with initial '!'
    treated as a negation operator.  This is forward-compatible to Git's
    ignore syntax and is a superset of Unix glob(3) syntax.

    *   matches any string of characters.
    ?   matches any single character.
    []  brackets a character class; it matches any character in the
        class.  So, for example, [0123456789] would match any decimal
        digit.
    [-] can be used to match ranges, e.g. [a-z] matches any lowercase letter.
    [^] brackets a negated character class; [^0123456789] would match
        any character not a decimal digit.
    [!] also brackets a negated character class
""",
}


def help_method(*args: str) -> None:
    "Summarize src commands, or (with argument) show help for a single command."
    if not args:
        sys.stdout.write(help_topics["topics"])
    for arg in args:
        if arg in help_topics:
            if sys.stdout.isatty():
                pydoc.pager(help_topics[arg])
            else:
                sys.stdout.write(help_topics[arg])
        else:
            croak("%s is not a known help topic.\n%s" % (arg, help_topics["topics"]))


def parse_as_revspec(token: str) -> bool:
    "Does this look like something that should be parsed as a revision spec?"
    if "/" in token:
        return False
    elif ".." in token:
        return True
    elif token.count("-") == 1 and "." not in token:
        return True
    elif token.isdigit():
        return True
    elif token.startswith("@"):  # Escape clause for tags that look like files
        return True
    else:
        return False


ignorable: set[str] | None = None
ignorable_dir: str | None = None


def ignore(filename: str) -> bool:
    "Should the specified file be ignored?"
    # pylint: disable=global-statement
    global ignorable, ignorable_dir
    here = os.getcwd()
    if ignorable is None or ignorable_dir != here:
        ignorable = set()
        ignorable_dir = here
        if os.path.exists(".srcignore"):
            with open(".srcignore", "rb") as fp:
                for line in fp:
                    line = polystr(line)
                    # Hack to make src a bit more compatible with
                    # other systems and POSIX glob(3).
                    line = line.replace("[^", "[!")
                    if line.startswith("#") or not line.strip():
                        continue
                    elif line.startswith("!"):
                        ignorable -= set(glob.glob(line[1:].strip()))
                    else:
                        ignorable |= set(glob.glob(line.strip()))
    return (
        (filename == repodir)
        or (os.path.basename(filename) in (RCS.RCS_LOCK, SCCS.SCCS_LOCK))
        or (filename in ignorable)
    )


# pycheck: disable=too-many-branches
class CommandContext:
    "Consume a revision specification or range from an argument list"

    # pylint: disable=too-many-arguments,too-many-branches,too-many-statements
    def __init__(
        self,
        cmd: str,
        args: Sequence[str],
        require_empty: bool = False,
        default_to: str | None = None,
        parse_revspec: bool = True,
        default_files: bool = True,
    ) -> None:
        self.start: int | str | None = None
        self.end: int | str | None = None
        self.seq: list[HistoryEntry] | None = None
        self.branchwise: bool | None = None
        if isinstance(args, tuple):
            args = list(args)
        self.args = list(args)
        self.default_to: str | None = default_to
        self.lo: int | None = self.start
        self.hi: int | None = self.end
        revspec: str | None = None
        if self.args:
            if self.args[0] == "--":
                parse_revspec = False
                self.args.pop(0)
            elif parse_revspec and parse_as_revspec(args[0]):
                revspec = self.args.pop(0)
                if revspec.startswith("@"):
                    revspec = revspec[1:]
                try:
                    if "-" in revspec or ".." in revspec:
                        self.branchwise = ".." in revspec
                        try:
                            (self.start, self.end) = revspec.split("-")
                        except ValueError:
                            try:
                                (self.start, self.end) = revspec.split("..")
                            except ValueError:  # pragma: no cover
                                croak("internal error - argument parser is confused")
                        try:
                            self.start = int(self.start)
                        except ValueError:  # pragma: no cover
                            pass
                        try:
                            self.end = int(self.end)
                        except ValueError:  # pragma: no cover
                            pass
                    else:
                        try:
                            self.end = self.start = int(revspec)
                        except ValueError:
                            self.end = self.start = revspec
                except ValueError:  # pragma: no cover
                    croak("malformed revision spec: %s" % revspec)
        if require_empty and not self.is_empty():
            croak("%s doesn't take a revision spec" % cmd)
        if self.args:
            if self.args[0] == "--":
                self.args.pop(0)
        if not self.args:
            if not default_files:
                croak("%s requires at least one file argument" % cmd)
            try:
                masters = [fn for fn in os.listdir(repodir) if backend.is_history(fn)]
                masters.sort()
            except OSError:
                croak("repo directory %s does not exist" % repodir)
            if masters:
                self.args += [backend.workfile(master) for master in masters]
            else:
                croak("%s requires at least one file argument" % cmd)
        if multidir and not quiet:
            announce("%s is selected." % repodir)

    def is_empty(self) -> bool:
        "Is the spec empty?"
        return self.start is None

    # def is_singleton(self):
    #    "Is the spec a singleton?"
    #    return self.start is not None and self.start == self.end

    def is_range(self) -> bool:
        "Is the spec a range?"
        return self.start is not None and self.start != self.end

    def select_all(self, metadata: History) -> None:
        "Set the range to all revisions."
        self.lo = 1
        self.hi = len(metadata)
        self.seq = [metadata.by_revno(i) for i in range(self.lo, self.hi + 1)]

    def select_tip(self, metadata: History) -> None:
        "Set the range to the tip revision."
        self.lo = len(metadata)
        self.hi = None
        self.seq = [metadata.by_revno(self.lo)]

    def __contains__(self, i: int) -> bool:
        "Does the spec contain the given revno?"
        if self.seq is None:
            croak(
                "revision spec hasn't been resolved"
            )  # pragma: no cover (should never happen)
        for item in self.seq:
            if item.revno == i:
                return True
        return False

    # pylint: disable=too-many-branches
    def resolve(self, metadata: History) -> list[HistoryEntry]:
        "Resolve a revision spec that may contain tags into revnos."
        if debug >= DEBUG_SEQUENCE:
            logit("Entering resolve with start=%s, end=%s\n" % (self.start, self.end))
        if self.is_empty():
            if debug >= DEBUG_SEQUENCE:
                logit("Revision spec is empty\n")
            if self.default_to == "branch":
                self.seq = metadata.current_branch_revisions(backwards=False)
            elif self.default_to == "branch_reversed":
                self.seq = metadata.current_branch_revisions(backwards=True)
            else:
                self.seq = []
            if debug >= DEBUG_SEQUENCE:
                logit(
                    "Empty revision spec returns %s\n" % ([x.revno for x in self.seq],)
                )
            return self.seq

        def subresolve(token: int | str | None) -> int:
            part = token
            if isinstance(part, int):
                return part
            if token == "":  # User specified @
                current = metadata.current()
                if current is None:
                    croak(
                        "in {0}, no current revision".format(metadata.filename)
                    )  # pragma: no cover (should never happen)
                return current.revno
            if part not in metadata.symbols:
                croak(
                    "in {0}, can't resolve symbol {1}".format(metadata.filename, token)
                )
            else:
                part = metadata.symbols[part]
            if backend.isbranch(part):
                part = backend.branch_to_tip(part, metadata)
            return metadata.native_to_revno(part)

        self.lo = subresolve(self.start)
        self.hi = subresolve(self.end)
        if debug >= DEBUG_SEQUENCE:
            logit("Subresolved range: lo=%s, hi=%s\n" % (self.lo, self.hi))
        # pylint: disable=superfluous-parens
        mreversed = self.lo > self.hi
        if mreversed:
            swapme = self.hi
            self.hi = self.lo
            self.lo = swapme
        if self.hi > len(metadata):
            croak("{0} has no {1} revision".format(metadata.filename, self.hi))
        if not self.branchwise:
            self.seq = [metadata.by_revno(i) for i in range(self.lo, self.hi + 1)]
        else:
            self.seq = []
            e = metadata.by_revno(self.hi)
            while True:
                self.seq.append(e)
                if e.revno == self.lo:
                    break
                if e.parent is None:
                    croak("%s is not an ancestor of %s" % (self.lo, self.hi))
                else:
                    e = e.parent
        if debug >= DEBUG_SEQUENCE:
            logit(
                "selection: %s, branchwise is %s\n"
                % ([x.revno for x in self.seq], "on" if self.branchwise else "off")
            )
            for item in metadata.revlist:
                logit("%s\t%s\t%s\n" % (item.revno, item.date, item.native))
        # Because in the branchwise case the sequence is generated in reverse
        if self.branchwise:
            self.seq.reverse()
        # Range might have been reversed
        if mreversed:
            self.seq.reverse()
        return self.seq


class CommentContext:
    "Encapsulate comment part of a revision."
    COMMENT_CUTLINE = """\
.............................................................................
"""
    COMMENT_EXPLANATION = """\
The cut line and things below it will not become part of the comment text.
"""

    def __init__(self, legend: str, args: list[str]) -> None:
        "Attempt to collect a comment from command line args."
        self.leader: str = ""
        self.comment: str | None = None
        self.force_edit: bool = False
        self.parse_revspec: bool = True
        while args:
            if args[0] == "--":
                self.parse_revspec = False
                args.pop(0)
                break
            elif args[0] == "-":
                self.leader = sys.stdin.read()
                args.pop(0)
            elif args[0] == "-e":
                self.force_edit = True
                args.pop(0)
            elif args[0] == "-m":
                args.pop(0)
                try:
                    self.leader = args[0] + "\n"
                    args.pop(0)
                except IndexError:  # pragma: no cover
                    croak("%s -m requires a following string" % legend)
            elif args[0].startswith("-m"):
                self.leader = args[0][2:] + "\n"
                args.pop(0)
            elif args[0] == "-f":
                args.pop(0)
                try:
                    filename = args[0]
                    # Read filesystem data as binary for robustness, but
                    # decode to Unicode for internal use
                    with open(filename, "rb") as fp:
                        self.leader = polystr(fp.read())
                    args.pop(0)
                except IndexError:  # pragma: no cover
                    croak("%s -f requires a following filename argument" % legend)
                except OSError:  # pragma: no cover
                    croak("couldn't open %s." % filename)
            elif args[0].startswith("-"):
                croak("unexpected %s option" % args[0])  # pragma: no cover
            else:
                break

    def edit(
        self,
        content: str = "",
        trailer: str = "",
        diff: Iterable[str] | None = None,
    ) -> bool:
        "Interactively edit a comment if required, then prepare for handoff."
        if self.leader and not self.force_edit:
            self.comment = self.leader
        else:
            orig_content = content
            if self.leader:
                content = self.leader + content
            if trailer or diff:
                content += (
                    "\n"
                    + CommentContext.COMMENT_CUTLINE
                    + CommentContext.COMMENT_EXPLANATION
                    + trailer
                )
            editor = os.getenv("EDITOR")
            if editor is None:  # pragma: no cover
                for editor in (
                    "emacsclient",
                    "emacs",
                    "vim",
                    "vi",
                    "nano",
                    "joe",
                    "jed",
                ):
                    if shutil.which(editor):
                        break
                else:
                    croak("can't find a text editor to launch")
            commentfile = None
            try:
                # Using latin-1 for passthrough isn't sufficient here.
                # The problem is that the trailer may contain real Unicode
                # characters rather than ASCII - this will happen if you
                # commit on a filename that Python decodes into Unicode.
                # Since we'll editing a comment and don't have to worry about
                # clobbering file content, temporatily enter UTF-8 land.
                with tempfile.NamedTemporaryFile(
                    prefix="src", suffix="tmp", delete=False
                ) as fp:
                    commentfile = fp.name
                    fp.write(polyutf8bytes(content))
                    if diff:
                        fp.write(b"\nChanges to be committed:\n")
                        for s in diff:
                            fp.write(polyutf8bytes(s))
                            fp.write(b"\n")
                do_or_die(editor + " " + shlex.quote(commentfile), "edit", mute=False)
                with open(commentfile, "rb") as fp:
                    self.comment = polyutf8str(fp.read())
            except IOError:  # pragma: no cover
                croak("edit aborted.")
            finally:
                if commentfile:
                    os.unlink(commentfile)
            where = self.comment.find(CommentContext.COMMENT_CUTLINE)
            if where != -1:
                self.comment = self.comment[:where]
            self.comment = self.comment.strip()
            if self.comment == orig_content.strip() or not self.comment:
                return False
            # Can be removed if we ever parse RCS/SCCS files directly
            for badnews in backend.delimiters:
                if badnews in self.comment:
                    croak("malformed comment")  # pragma: no cover
        if not self.comment.endswith("\n"):
            self.comment += "\n"
        return True

    def content(self) -> str:
        "Return the edited comment."
        return self.comment


# pylint: disable=too-many-arguments
def external_diff(
    file0: str,
    s0: str | bytes,
    file1: str,
    s1: str | bytes,
    unified: bool = True,
    ignore_ws: str | None = None,
) -> list[str]:
    "Compute diff using external program."

    def writetmp(s: str | bytes) -> str:
        with tempfile.NamedTemporaryFile(
            prefix="src", suffix="tmp", delete=False
        ) as fp:
            fp.write(polybytes(s))
            return fp.name

    if unified:
        opts, tok0, tok1 = "-u", "-", "+"
    else:
        opts, tok0, tok1 = "-c", "*", "-"
    if ignore_ws:
        opts += " " + ignore_ws
    tmp0 = tmp1 = None
    try:
        tmp0 = writetmp(s0)
        tmp1 = writetmp(s1)
        with popen_or_die(
            command='diff %s "%s" "%s" || :' % (opts, tmp0, tmp1),
            legend="external diff",
        ) as fp:
            diff = polystr(fp.read())
    finally:
        for p in (tmp0, tmp1):
            if p and os.path.exists(p):
                os.unlink(p)
    diff = re.sub(r"(?m)^([%s]{3} ).+$" % tok0, r"\1" + file0, diff, 1)
    diff = re.sub(r"(?m)^([%s]{3} ).+$" % tok1, r"\1" + file1, diff, 1)
    return diff.split("\n")


def compute_diff(
    metadata: Any,
    lo: int | None,
    hi: int | None,
    differ: Callable[..., Iterable[str]],
    ignore_ws: str | None = None,
) -> Iterable[str]:
    """Compute diff between two revs of a file.
    If 'lo' is None, then this is a "creation event" in which 'hi'
    materializes fully formed from nothing.
    If 'hi' is None, then diff 'lo' against the working file.
    File must already have been "lifted"."""
    name = metadata.filename
    if lo is None:
        file0 = "/dev/null"
        old_content = ""
    else:
        file0 = name + " (r" + str(lo) + ")"
        with backend.cat(name, metadata.revno_to_native(lo)) as fp:
            old_content = fp.read()  # this data will be binary
    if hi is None:
        file1 = name + " (workfile)"
        with open(name, "rb") as fp:
            new_content = fp.read()
    else:
        file1 = name + " (r" + str(hi) + ")"
        with backend.cat(name, metadata.revno_to_native(hi)) as fp:
            new_content = fp.read()  # this data will be binary
    # Don't list identical files (comparison uses binary data
    # for maximum accuracy).
    if old_content == new_content:
        return ()
    if ignore_ws:
        return external_diff(
            file0,
            old_content,
            file1,
            new_content,
            differ == difflib.unified_diff,
            ignore_ws,
        )
    lines0 = polystr(old_content).split("\n")
    lines1 = polystr(new_content).split("\n")
    return differ(lines0, lines1, fromfile=file0, tofile=file1, lineterm="")


def colorize_unified(s: str) -> str:
    for x in colorize_unified.colors:
        if s.startswith(x[0]):
            return x[1] + s + RESET
    return s


colorize_unified.colors = (
    ("+++ ", BOLD),
    ("--- ", BOLD),
    ("@@ ", CCYAN),
    ("+", CGREEN),
    ("-", CRED),
)


def print_diff(
    metadata: History,
    lo: int | None,
    hi: int | None,
    differ: Callable[..., Iterable[str]],
    ignore_ws: str | None = None,
) -> None:
    "Dump diff between revisions to standard output."
    if differ == difflib.unified_diff:
        colorizer = colorize_unified
    else:
        colorizer = lambda x: x
    with backend.manager(metadata.filename):
        for line in compute_diff(metadata, lo, hi, differ, ignore_ws):
            sys.stdout.write(colorizer(line) + "\n")


def exec_copy(source: str, target: str) -> None:
    if os.path.exists(target):
        oldtargetmode = newtargetmode = os.stat(target).st_mode
        sourcemode = os.stat(source).st_mode
        for bitmask in (stat.S_IXUSR, stat.S_IXGRP, stat.S_IXOTH):
            if bitmask & sourcemode:
                newtargetmode |= bitmask
            else:
                newtargetmode &= ~bitmask
        if newtargetmode != oldtargetmode:
            os.chmod(target, newtargetmode)


def checkout_method(*args: str) -> None:
    "Refresh the working copy from the history file."
    ctx = CommandContext("checkout", args, default_files=False)
    if ctx.is_range():
        croak("checkout needs an empty or singleton revision spec")
    for arg in ctx.args:
        metadata = History(arg)
        ctx.resolve(metadata)
        selected = None
        if ctx.is_empty():
            selected = metadata.tip()
            # An empty checkout spec should use the backend's native "current tip"
            # operation rather than being rewritten into an explicit native revision.
            # SCCS distinguishes between `get -e` and `get -e -rSID`, and the latter
            # can interact differently with prior checkout state.  RCS also doesn't
            # need a revision specified to check out tip, but won't become subtly
            # deranged if you specify one.
            revision = None
        elif ctx.lo > len(metadata):
            croak("%s has only %d revisions" % (arg, len(metadata)))
        else:
            selected = metadata.by_revno(ctx.lo)
            revision = selected.native
        with backend.manager(arg) as xc:
            backend.checkout(xc.pathbase, revision)
            if backend.has_branches and selected is not None:
                backend.set_branch(
                    backend.revision_to_branch(selected.native), xc.pathbase
                )
        if not quiet and len(args) > 1 and selected is not None:
            announce("%s <- %d" % (metadata.reportme(), selected.revno))


# pylint: disable=unused-argument
def init_method(*args: str) -> None:
    "Initialize a repository directory."
    # pylint: disable=unnecessary-pass
    pass


# pylint: disable=too-many-branches,too-many-statements
def commit_method(*args: str) -> None:
    "Commit changes to files."
    args = list(args)
    register_only = False
    parse_revspec = True
    branch = None
    differ = difflib.unified_diff
    while args:
        if args[0] == "--":
            args.pop(0)
            parse_revspec = False
            break
        elif args[0] == "-a":
            # Perform error check, but don't actually do a commit.
            # The Emacs VC-mode support for SRC was written early,
            # before 1.0, when I hadn't quite figured out what the
            # most efficient method for file registration would be.
            # VC-mode wants to have a registration as well as a
            # checkin method. This is no longer needed for normal SRC
            # operation, but it's better to leave this in place than
            # risk causing hassles for people running old Emacs versions.
            register_only = True
            parse_revspec = False
            args.pop(0)
        elif args[0] == "-b":
            args.pop(0)
            if not args:
                croak("commit -b requires a following branch name")
            branch = args.pop(0)
        else:
            break
    comment = None  # pacify pylint
    if not register_only:
        comment = CommentContext("commit", args)
    ctx = CommandContext(
        "commit",
        args,
        require_empty=True,
        parse_revspec=parse_revspec and comment.parse_revspec,
    )
    for arg in ctx.args:
        if not os.path.exists(arg):
            croak("I see no '%s' here." % arg)
        if os.path.isdir(arg):
            croak("cannot commit directory '%s'" % arg)
        if branch is not None and not registered(arg):
            croak("can't set branch on unregistered file.")
    for arg in ctx.args:
        trailer = None  # Pacify pylint
        diff = None  # Pacify pylint
        if not registered(arg):
            trailer = "Committing initial revision of {0}.\n".format(arg)
            revcount = 0
            metadata = None
            diff = compute_diff(type("", (), {"filename": arg}), None, None, differ)
        elif register_only:
            croak("attempt to re-add a registered file failed")
        else:
            metadata = History(arg)
            ctx.resolve(metadata)
            if metadata and ctx.is_empty():
                ctx.select_tip(metadata)
            revcount = len(metadata)
            trailer = "Committing {0} revision {1}.\n".format(
                metadata.reportme(), revcount + 1
            )
            with backend.manager(arg):
                diff = compute_diff(metadata, ctx.lo, None, differ)
        if not register_only and not diff:
            announce("in %s, no changes to commit" % arg)
            continue
        if not register_only and not comment.edit("", trailer, diff):
            announce("in %s, commit cancelled" % arg)
        else:
            has_history = registered(arg)
            if not has_history:
                if debug >= DEBUG_COMMANDS:
                    logit("registration phase:\n")
                # We can't use the manager here, it wants to go clear down
                # to a repository directory.
                try:
                    d = os.path.dirname(arg)
                    if d:
                        chdir(d, "before registering")
                    backend.register(os.path.basename(arg))
                finally:
                    if d:
                        chdir(startdir, "after registering")
            if debug >= DEBUG_COMMANDS:
                logit("commit phase:\n")
            if not register_only:
                with backend.manager(arg) as xc:
                    # If the user changed the executable bit while
                    # modifying the workfile, propagate this change to
                    # the master.  Without this hack, the sequence (1)
                    # Commit workfile (2) Make workfile executable, (3)
                    # checkin workfile fails to work as expected because
                    # the VCS doesn't propagate the changed executable
                    # bit to the master, leading to misbehavior on the
                    # next checkout.
                    exec_copy(xc.pathbase, backend.history(xc.pathbase))
                    if branch is not None:
                        if not has_history:
                            croak("can't set branch on unregistered file.")
                        if branch not in metadata.symbols:
                            croak("can't switch to nonexistent branch %s." % branch)
                        elif not backend.isbranch(metadata.symbols[branch]):
                            croak("%s is not a branch." % branch)
                        if backend.has_branches:
                            backend.set_branch(
                                metadata.symbols[branch], metadata.filename
                            )
                    backend.checkin(xc.pathbase, comment.content())
            if metadata is None:
                metadata = History(arg)
            if not quiet and len(args) > 1:
                announce("%s -> %d" % (metadata.reportme(), revcount + 1))


def add_method(*args: str) -> None:
    "For Emacs VC compatibility."
    commit_method("-a", *args)


def amend_method(*args: str) -> None:
    "Amend comments in stored revisions."
    if not os.path.exists(repodir):
        croak("repository subdirectory %s does not exist" % repodir)
    args = list(args)
    differ = difflib.unified_diff
    comment = CommentContext("amend", args)
    ctx = CommandContext("amend", args, parse_revspec=comment.parse_revspec)
    if ctx.is_range():
        croak("amend cannot take a range")
    for arg in ctx.args:
        if not registered(arg):
            croak("%s is not registered." % arg)
        elif not os.path.exists(arg):
            croak("I see no '%s' here." % arg)
    for arg in ctx.args:
        metadata = History(arg)
        ctx.resolve(metadata)
        if ctx.is_empty():
            ctx.lo = metadata.tip().revno
        trailer = "Amending {0} revision {1}.\n".format(arg, ctx.lo)
        item = metadata.by_revno(ctx.lo)
        parent = item.parent.revno if item.parent else None
        with backend.manager(arg):
            diff = compute_diff(metadata, parent, ctx.lo, differ)
        if not comment.edit(metadata.by_revno(ctx.lo).log, trailer, diff):
            announce("in %s, amend cancelled" % metadata.reportme())
        else:
            with backend.manager(arg) as xc:
                backend.amend(
                    xc.pathbase, metadata.revno_to_native(ctx.lo), comment.content()
                )
        if not quiet and len(args) > 1:
            announce("%s : %d" % (metadata.reportme(), ctx.lo))


def uncommit_method(*args: str) -> None:
    "Remove the last commit, leaving the workfile unaltered."
    if not os.path.exists(repodir):
        croak("repository subdirectory %s does not exist" % repodir)
    if not args or (len(args) == 1 and args[0] == "--"):
        croak("uncommit requires at least one file argument")
    ctx = CommandContext("uncommit", args, require_empty=True)
    for arg in ctx.args:
        if not registered(arg):
            croak("%s is not registered." % arg)
        elif not os.path.exists(arg):
            croak("I see no '%s' here." % arg)
    for arg in ctx.args:
        metadata = History(arg)
        if not metadata.revlist:
            croak("%s has no revisions" % arg)
        tip = metadata.tip()
        # RCS requires the branch tip to be the currently checked-out revision
        # before it can be removed.  SCCS uncommit handles any required unedit
        # internally, so it must not be blocked by the same precondition.
        # FIXME: Unclean chumminess with back end
        if backend == RCS:
            if not metadata.lockrevs or metadata.lockrevs[0] != tip.native:
                croak("can only uncommit the branch tip; checkout tip first")
        with backend.manager(arg) as xc:
            backend.uncommit(xc.pathbase, tip.native)
        if not quiet and len(args) > 1:
            announce("%s <- %d" % (metadata.reportme(), tip.revno))


def list_method(*args: str) -> None:
    "Generate a summary listing of commits, one line per commit."
    args = list(args)
    custom = None
    limit = None
    porcelain = False
    parse_revspec = True
    while args and args[0].startswith("-"):
        if args[0] == "--":
            parse_revspec = False
            args.pop(0)
            break
        elif args[0] == "-P":
            porcelain = True
            args.pop(0)
        elif args[0] == "-f":
            args.pop(0)
            try:
                custom = args[0]
                args.pop(0)
            except IndexError:  # pragma: no cover
                croak("list -f requires a following string")
        elif args[0].startswith("-f"):
            # This case is used internally by Emacs VC mode. Don't remove it!
            custom = args[0][2:]
            args.pop(0)
        elif args[0] == "-l":
            args.pop(0)
            try:
                limit = args[0]
                args.pop(0)
                limit = int(limit)
            except IndexError:  # pragma: no cover
                croak("list -l requires a following integer")
            except ValueError:  # pragma: no cover
                croak("%s is not an integer" % limit)
        elif args[0][1:].isdigit():
            limit = int(args.pop(0)[1:])  # it's all digits, so no ValueError
        else:
            croak("unexpected %s option" % args[0])
    if porcelain and custom is not None:
        croak("list -P cannot be combined with -f")
    ctx = CommandContext(
        "list", args, default_to="branch_reversed", parse_revspec=parse_revspec
    )
    for arg in ctx.args:
        if ignore(arg) or os.path.isdir(arg) or not registered(arg):
            continue
        if not porcelain and custom is None:
            sys.stdout.write("= %s %s\n" % (arg, ((WIDTH - len(arg) - 3) * "=")))
        for item in ctx.resolve(History(arg)):
            # Must allow enough room for revno and date
            if item.selected():
                mark = "*"
            else:
                mark = "-"
            summary = item.log.split("\n")[0]
            if porcelain:
                emit_tabular((arg, item.revno, mark, item.getdate("author"), summary))
            elif custom is None:
                summary = summary[: WIDTH - 34]
                sys.stdout.write(
                    "%-4d  %s %s %s\n"
                    % (item.revno, mark, item.getdate("author"), summary)
                )
            else:
                sys.stdout.write(
                    custom.format(
                        arg, item.revno, mark, item.getdate("author"), summary
                    )
                    + "\n"
                )
            if limit is not None:
                limit -= 1
                if limit <= 0:
                    break


def log_method(*args: str) -> None:
    "Report revision logs"
    limit = None
    args = list(args)
    parse_revspec = True
    differ = None
    ignore_ws = None
    verbose = 0
    porcelain = False
    while args and args[0].startswith("-"):
        if args[0] == "--":
            parse_revspec = False
            args.pop(0)
            break
        elif args[0] == "-P":
            porcelain = True
            args.pop(0)
        elif args[0] == "-l":
            args.pop(0)
            try:
                limit = args[0]
                args.pop(0)
                limit = int(limit)
            except IndexError:  # pragma: no cover
                croak("list -l requires a following integer")
            except ValueError:  # pragma: no cover
                croak("%s is not an integer" % limit)
        elif args[0][1:].isdigit():
            limit = int(args.pop(0)[1:])  # it's all digits, so no ValueError
        elif args[0] in ("--patch", "-p", "-u"):
            differ = difflib.unified_diff
            args.pop(0)
        elif args[0] == "-c":
            differ = difflib.context_diff
            args.pop(0)
        elif args[0] in ("-b", "-w"):
            ignore_ws = args.pop(0)
        elif args[0] == "-v":
            verbose += 1
            args.pop(0)
        else:
            croak("unexpected %s option" % args[0])
    if porcelain and differ is not None:
        croak("log -P cannot be combined with patch output")
    ctx = CommandContext(
        "log", args, default_to="branch_reversed", parse_revspec=parse_revspec
    )
    # pylint: disable=too-many-nested-blocks
    for arg in ctx.args:
        if ignore(arg) or os.path.isdir(arg) or not registered(arg):
            continue
        if not porcelain:
            sys.stdout.write("= %s %s\n" % (arg, ((WIDTH - len(arg) - 3) * "=")))
        metadata = History(arg)
        for item in ctx.resolve(metadata):
            if porcelain:
                record: list[object] = [
                    arg,
                    item.revno,
                    item.getdate("author"),
                    item.branch,
                    item.log,
                ]
                if verbose and item.headers:
                    headers = item.headers
                    if verbose == 1:
                        headers = {}
                        for k in ("author", "committer"):
                            if k in item.headers:
                                v = item.headers[k]
                                if k + "-date" in item.headers:
                                    v += " " + item.headers[k + "-date"]
                                headers[k] = v
                    headertext = "".join(
                        "%s: %s\n" % (k.title(), headers[k])
                        for k in sorted(headers.keys())
                    )
                    record.append(headertext)
                emit_tabular(record)
            else:
                sys.stdout.write(
                    "%s%-4d%s | %s%s%s | %s%s%s\n"
                    % (
                        BOLD + CCYAN,
                        item.revno,
                        RESET,
                        CYELLOW,
                        item.getdate("author"),
                        RESET,
                        BOLD + CGREEN,
                        item.branch,
                        RESET,
                    )
                )
            if verbose and item.headers:
                headers = item.headers
                if verbose == 1:
                    headers = {}
                    for k in ("author", "committer"):
                        if k in item.headers:
                            v = item.headers[k]
                            if k + "-date" in item.headers:
                                v += " " + item.headers[k + "-date"]
                            headers[k] = v
                if not porcelain:
                    for k in sorted(headers.keys()):
                        sys.stdout.write(
                            "%s%s%s: %s\n" % (BOLD, k.title(), RESET, headers[k])
                        )
                    sys.stdout.write("\n")
            if not porcelain:
                sys.stdout.write("%s" % item.log)
            if differ and not porcelain:
                if item.parent:
                    parent = item.parent.revno
                    pdesc = "r%d/%s" % (parent, arg)
                else:
                    parent = None
                    pdesc = "/dev/null"
                sys.stdout.write(
                    "\n%sdiff %s r%s/%s%s\n" % (BOLD, pdesc, item.revno, arg, RESET)
                )
                print_diff(metadata, parent, item.revno, differ, ignore_ws)
            if not porcelain:
                sys.stdout.write(("-" * WIDTH) + "\n")
            if limit is not None:
                limit -= 1
                if limit <= 0:
                    break


def status_method(*args: str) -> None:
    "Get status of some or all files."
    args = list(args)
    allflag = False
    qflag = False
    while args:
        if args[0] == "--":
            args.pop(0)
            break
        elif args[0] == "-a":
            allflag = True
            args.pop(0)
        elif args[0] == "-q":
            qflag = True
            args.pop(0)
        else:
            break
    # No command context is created, so we do this explicitly
    if multidir and not quiet:
        announce("%s is selected." % repodir)
    if args:
        candidates = args
    else:
        candidates = []
        for dirpath, _, fnames in os.walk("./"):
            # This prevents the search from blowing up on large directories that have a lot
            # of subdirectories that aren't SRC-controlled.
            if (
                (not os.path.exists(os.path.join(dirpath, ".src")))
                and (not os.path.exists(os.path.join(dirpath, "RCS")))
                and (not os.path.exists(os.path.join(dirpath, "SCCS")))
            ):
                continue
            for f in fnames:
                candidates.append(os.path.join(dirpath, f)[2:])
    pairs = []
    for fn in candidates:
        if backend.is_history(fn):
            if not os.path.isfile(backend.workfile(fn)):
                pairs.append((fn, "!"))
        elif ignore(fn):
            if allflag or fn in args:
                pairs.append((fn, "I"))
        elif not os.path.isfile(backend.history(fn)):
            if not qflag:
                pairs.append((fn, "?"))
        elif not os.path.exists(fn):
            pairs.append((fn, "!"))
        elif modified(fn):
            pairs.append((fn, "M"))
        elif not os.access(fn, os.W_OK):
            pairs.append((fn, "L"))
        elif not backend.has_revisions(fn):
            pairs.append((fn, "A"))
        else:
            pairs.append((fn, "="))
    pairs.sort()
    for fn, status in pairs:
        sys.stdout.write(status + "  " + fn + "\n")


def cat_method(*args: str) -> None:
    "Dump revision content to standard output."
    ctx = CommandContext("cat", args)
    if ctx.is_range():
        croak("cat refuses to cough up a hairball")
    for arg in ctx.args:
        metadata = History(arg)
        ctx.resolve(metadata)
        if ctx.is_empty():
            ctx.select_tip(metadata)
        with backend.manager(arg) as xc:
            for item in ctx.seq:
                with backend.cat(xc.pathbase, item.native) as fp:
                    sys.stdout.write(polystr(fp.read()))


def diff_method(*args: str) -> None:
    "Dump diffs between revisions to standard output."
    if isinstance(args, tuple):
        args = list(args)
    differ = difflib.unified_diff
    ignore_ws = None
    while args and args[0] != "--" and args[0].startswith("-"):
        if args[0] == "-u":
            differ = difflib.unified_diff
            args.pop(0)
        elif args[0] == "-c":
            differ = difflib.context_diff
            args.pop(0)
        elif args[0] in ("-b", "-w"):
            ignore_ws = args.pop(0)
        else:
            croak("unexpected %s option" % args[0])
    ctx = CommandContext("diff", args)
    for arg in ctx.args:
        metadata = History(arg)
        ctx.resolve(metadata)
        if ctx.is_empty():
            ctx.select_tip(metadata)
        print_diff(metadata, ctx.lo, ctx.hi, differ, ignore_ws)


# pylint: disable=too-many-locals,too-many-nested-blocks
def tag_helper(
    args: Sequence[str],
    legend: str,
    validation_hook: Callable[[CommandContext, History, str], str | None],
    delete_method: Callable[[str, History], int],
    set_method: Callable[[str, str | None, History], Any],
) -> None:
    "Dispatch to handlers for tag and branch manipulation."
    if not os.path.exists(repodir):
        croak("repository subdirectory %s does not exist" % repodir)
    args = list(args)
    if not args:
        args = ["list"] + args
    if args[0] == "--":
        args.pop(0)
    else:
        if args[0] in ("-d", "del", "delete"):
            args.pop(0)
            if not args:
                croak("%s deletion requires a name argument" % legend)
            name = args.pop(0)
            ctx = CommandContext(legend + " deletion", args, default_files=False)
            if not ctx.is_empty():
                croak(
                    "can't accept a revision-spec when deleting a %s." % legend
                )  # pragma: no cover (should never happen)
            for arg in ctx.args:
                metadata = History(arg)
                if name not in metadata.symbols:
                    croak("in %s, %s is not a symbol" % (arg, name))
                elif backend.isbranch(metadata.symbols[name]) != (legend == "branch"):
                    croak("in %s, %s is not a %s" % (arg, name, legend))
                else:
                    if legend == "branch":
                        current_branch = metadata.symbols[name]
                        for lock in metadata.lockrevs:
                            if backend.revision_to_branch(lock) == current_branch:
                                croak("can't delete the current branch")
                    status = 0
                    with backend.manager(arg) as xc:
                        status = delete_method(name, metadata)
                    if status != 0:
                        croak("%s deletion failed." % legend)
                    if not quiet and len(args) > 1:
                        announce("in %s, %s %s removed" % (xc.pathbase, legend, name))
            return
        if args[0] in ("-l", "list"):
            args.pop(0)
            ctx = CommandContext(legend + " listing", args, require_empty=True)
            for arg in ctx.args:
                metadata = History(arg)
                ctx.resolve(metadata)
                if ctx.is_empty():
                    prepend = [0]
                    ctx.select_all(metadata)
                else:
                    prepend = []
                revisions = prepend + [item.revno for item in ctx.seq]
                sys.stdout.write("= %s %s\n" % (arg, ((WIDTH - len(arg) - 5) * "=")))
                keys = list(metadata.symbols.keys())
                if metadata.tipbranch in keys:
                    keys.remove(metadata.tipbranch)
                    keys.sort()
                    keys = [metadata.tipbranch] + keys
                for key in keys:
                    value = metadata.symbols[key]
                    selected = ""
                    if legend == "branch":
                        # Note!  This code relies on
                        # backend.branch_to_parent() returning an empty
                        # string when called on a trunk revision.
                        displaystr = backend.branch_to_parent(value)
                        if not displaystr:
                            display = 0
                        else:
                            display = metadata.native_to_revno(displaystr)
                        selected = "* " if key == metadata.tipbranch else "- "
                    else:
                        display = metadata.native_to_revno(value)
                    if display in revisions and backend.isbranch(value) == (
                        legend == "branch"
                    ):
                        sys.stdout.write("%4s\t%s%s\n" % (display, selected, key))
            return
        if args[0] in ("-c", "create"):
            args.pop(0)
            if not args:
                croak("%s setting requires a name argument" % legend)
            name = args.pop(0)
            ctx = CommandContext(legend, args)
            if ctx.is_range():
                croak("can't accept a range when setting a %s" % legend)
            for arg in ctx.args:
                metadata = History(arg)
                revision = validation_hook(ctx, metadata, name)
                with backend.manager(arg) as xc:
                    set_method(name, revision, metadata)
                    if not quiet and len(args) > 1:
                        announce(
                            "in %s, %s %s = %s" % (xc.pathbase, legend, name, ctx.start)
                        )
            return


def tag_method(*args: str) -> None:
    "Inspect, create, and delete tags."

    def tag_set_validate(ctx: CommandContext, metadata: History, name: str) -> str:
        ctx.resolve(metadata)
        if name in metadata.symbols:
            croak("tag %s already set." % name)
        if ctx.is_empty():
            ctx.select_tip(metadata)
        return metadata.revno_to_native(ctx.lo)

    tag_helper(args, "tag", tag_set_validate, backend.delete_tag, backend.set_tag)


def branch_method(*args: str) -> None:
    "Inspect, create, and delete branches."

    def branch_set_validate(
        ctx: CommandContext, _metadata: History, _name: str
    ) -> None:
        if not ctx.is_empty():
            croak("cannot accept a revision after a branch name")

    tag_helper(
        args, "branch", branch_set_validate, backend.delete_branch, backend.make_branch
    )


def rename_method(*args: str) -> None:
    "Rename a branch or tag."
    args = list(args)
    if not args or args[0] not in ("tag", "branch"):
        croak("rename requires a following 'tag' or 'branch'")
    legend = args.pop(0)
    if not args:
        croak("rename requires a source name argument")
    name = args.pop(0)
    if not args:
        croak("rename requires a target name argument")
    newname = args.pop(0)
    ctx = CommandContext(
        legend + " renaming", args, require_empty=True, parse_revspec=False
    )
    for arg in ctx.args:
        metadata = History(arg)
        if name not in metadata.symbols:
            croak("in %s, cannot rename nonexistent %s %s" % (arg, legend, name))
        if newname in metadata.symbols:
            croak("in %s, cannot rename to existing %s %s" % (arg, legend, name))
        # In the case of a branch, we want to change only the
        # tag reference.
        with backend.manager(arg):
            backend.set_tag(newname, metadata.symbols[name], metadata)
            backend.delete_tag(name, metadata)
        if not quiet and len(args) > 1:
            announce("in %s, %s -> %s" % (arg, name, newname))


def filecmd(legend: str, hook: Callable[[str, str], Any], args: Sequence[str]) -> None:
    if not args or (len(args) == 1 and args[0] == "--"):
        croak("%s requires explicit source and target file arguments" % legend)
    ctx = CommandContext(
        legend, args, require_empty=True, parse_revspec=False, default_files=False
    )
    args = ctx.args
    if len(args) != 2:
        croak("%s requires exactly two arguments" % legend)
    (source, target) = args
    if not os.path.exists(source):
        croak("I see no '%s' here." % source)
    elif os.sep in target and not os.path.exists(os.path.dirname(target)):
        croak("directory '%s' does not exist." % os.path.dirname(target))
    elif not registered(source):
        croak("%s is not registered" % source)
    elif registered(target):
        croak("%s is registered, I won't step on it" % target)
    elif os.path.exists(target):
        croak(
            "%s exists, please delete manually if you want it gone" % target
        )  # pragma: no cover
    else:
        hook(source, target)


def move_method(*args: str) -> None:
    "Move a file and its history."
    filecmd("move", backend.move, args)


def copy_method(*args: str) -> None:
    "Copy a file and its history."
    filecmd("copy", backend.copy, args)


def release_method(*args: str) -> None:  # pragma: no cover
    "Release locks."
    ctx = CommandContext("release", args, require_empty=True)
    for arg in ctx.args:
        if not os.path.exists(arg):
            croak("I see no '%s' here." % arg)
        elif not registered(arg):
            croak("%s is not registered, skipping" % arg)
        else:
            with backend.manager(arg) as xc:
                backend.release(xc.pathbase)


def srcify_method(*args: str) -> None:
    "Move an RCS or SCCS directory into SRC management."
    if os.path.exists(".src"):
        croak("A %s directory already exists." % repodir)
    if args:
        croak("lift cannot accept arguments")
    if not os.path.isdir("RCS") and not os.path.isdir("SCCS"):
        croak("no RCS or SCCS directory")
    candidates = [
        f for f in os.listdir(".") if os.path.isfile(f) and not os.path.islink(f)
    ]
    for fn in candidates:
        if registered(fn) and (not os.path.exists(fn) or not modified(fn)):
            with backend.manager(fn) as xc:
                backend.checkout(xc.pathbase, "")
    if os.path.isdir("RCS"):
        rename("RCS", ".src", "in srcify")


def ls_method(*args: str) -> None:
    "List registered files."
    if args:
        croak("ls cannot accept arguments")
    try:
        masters = [fn for fn in os.listdir(repodir) if backend.is_history(fn)]
    except OSError:
        croak("repo directory %s does not exist" % repodir)
    masters.sort()
    for master in masters:
        sys.stdout.write(backend.workfile(master) + "\n")


def visualize_method(*args: str) -> None:
    "Generate (and possibly display) a DOT visualization of repo structure."
    if not os.path.exists(repodir):
        croak("repository subdirectory %s does not exist" % repodir)
    args = list(args)
    comment = CommentContext("visualize", args)
    ctx = CommandContext("visualize", args, parse_revspec=comment.parse_revspec)
    for arg in ctx.args:
        # if not os.path.exists(arg):
        #    croak("I see no '%s' here." % arg)
        if not registered(arg):
            croak("%s is not registered." % arg)
    for arg in ctx.args:
        metadata = History(arg)
        ctx.resolve(metadata)
        if ctx.is_empty():
            ctx.select_all(metadata)
        sys.stdout.write("digraph {\n")
        if len(ctx.args) > 1:
            pref = arg + ":"
        else:
            pref = ""
        for item in ctx.seq:
            if item.parent:
                sys.stdout.write(
                    "\t%s%d -> %s%d;\n" % (pref, item.parent.revno, pref, item.revno)
                )
            summary = htmlescape(item.log.split("\n")[0][:42])
            sys.stdout.write(
                '\t%s%s [shape=box,width=5,label=<<table cellspacing="0" border="0" cellborder="0"><tr><td><font color="blue">%s%s</font></td><td>%s</td></tr></table>>];\n'
                % (pref, item.revno, pref, item.revno, summary)
            )
            if metadata.tip(item.native) == item:
                sys.stdout.write(
                    '\t"%s%s" [shape=oval,width=2];\n' % (pref, item.branch)
                )
                sys.stdout.write(
                    '\t"%s%s" -> "%s%s" [style=dotted];\n'
                    % (pref, item.revno, pref, item.branch)
                )
        keys = sorted(metadata.symbols.keys())
        for name in keys:
            native = metadata.symbols[name]
            branch_label = backend.isbranch(native)
            if branch_label:
                native = backend.branch_to_tip(native, metadata)
            revno = metadata.native_to_revno(native)
            if not branch_label:
                sys.stdout.write(
                    '\t{rank=same; "%s%s"; "%s%s"}\n' % (pref, name, pref, revno)
                )
                sys.stdout.write(
                    '\t"%s%s" -> "%s%s" [style=dotted];\n' % (pref, name, pref, revno)
                )
        sys.stdout.write("}\n")


# pylint: disable=too-many-locals
def fast_export_method(*args: str) -> None:
    "Dump revision content to standard output."

    def fi_quote(path: str) -> str:
        "Quote path for git fast-import if needed."
        if not path:
            return '""'
        if not any(c in path for c in (" ", "\t", "\n", '"', "\\")):
            return path
        escaped = (
            path.replace("\\", "\\\\")
            .replace('"', '\\"')
            .replace("\n", "\\n")
            .replace("\t", "\\t")
            .replace("\r", "\\r")
        )
        return '"' + escaped + '"'

    def sanitize_tag(name: str) -> str:
        "Sanitize tag names for git fast-import refs."
        original = name
        sanitized = re.sub(r"\s+", "_", name)
        for c in "~^\\*?:":
            sanitized = sanitized.replace(c, "")
        sanitized = sanitized.replace("..", "_").replace("@{", "_")
        sanitized = sanitized.strip("./")
        if not sanitized:
            croak("tag name %s is ill-formed" % original)
        if sanitized != original:
            announce("tag name %s sanitized to %s" % (original, sanitized))
        return sanitized

    def attribute(item: HistoryEntry, who: str, fallback: str) -> str:
        s = fallback
        if item.headers and who in item.headers:
            s = item.headers[who]
        t, o = item.unixtime(who)
        hours, minutes = divmod(abs(o) // 60, 60)
        return "%s %s %d %s%02d%02d\n" % (
            who,
            s,
            t,
            "-" if o < 0 else "+",
            hours,
            minutes,
        )

    ctx = CommandContext("fast-export", args)
    mark = 0
    if pseudotime:
        username = "J. Random Hacker"
        useremail = "jrh@nowhere.man"
    else:
        username = polystr(capture_or_die("git config --get user.name")).strip()
        useremail = polystr(capture_or_die("git config --get user.email")).strip()
    attribution = "%s <%s>" % (username, useremail)
    markmap: dict[int, int] = {}
    tips: dict[str, int] = {}
    last_commit_mark = 0

    # This is meant to be consumed by reposurgeon's importer
    sys.stdout.write(
        "#sourcetype %s\n" % {"RCS": "rcs", "SCCS": "sccs"}.get(repodir, "src")
    )
    for arg in ctx.args:
        if not registered(arg):
            croak("%s is not registered" % arg)
        executable = os.stat(backend.history(arg)).st_mode & stat.S_IXUSR
        if executable:
            perms = "100755"
        else:
            perms = "100644"
        metadata = History(arg)
        ctx.resolve(metadata)
        if ctx.is_empty():
            ctx.select_all(metadata)
        tagmap: dict[int, list[str]] = {}
        tagname_seen: dict[str, str] = {}
        for key, val in list(metadata.symbols.items()):
            revno = None
            if backend.isbranch(val):
                if (
                    isinstance(backend, RCS)
                    and val == "1"
                    and key not in (metadata.tipbranch, "trunk")
                ):
                    revno = metadata.native_to_revno(backend.branch_to_base(val))
                else:
                    continue
            else:
                revno = metadata.native_to_revno(val)
            if revno is not None and revno in ctx:
                sanitized = sanitize_tag(key)
                if sanitized in tagname_seen and tagname_seen[sanitized] != key:
                    croak(
                        "tag name %s collides with %s after sanitization"
                        % (key, tagname_seen[sanitized])
                    )
                tagname_seen[sanitized] = key
                tagmap.setdefault(revno, []).append(sanitized)
        for tags in tagmap.values():
            tags.sort()
        primary_tag = None
        if ctx.lo in tagmap:
            primary_tag = tagmap[ctx.lo][0]
            tagmap[ctx.lo] = tagmap[ctx.lo][1:]
            if not tagmap[ctx.lo]:
                del tagmap[ctx.lo]
        with backend.manager(arg) as xc:
            for i in range(ctx.lo, ctx.hi + 1):
                item = metadata.by_revno(i)
                with backend.cat(xc.pathbase, item.native) as fp:
                    content = fp.read()  # this data will be binary
                size = len(content)  # size will be # of bytes, as desired
                mark += 1
                markmap[item.revno] = mark
                sys.stdout.write("blob\nmark :%d\ndata %d\n" % (mark, size))
                sys.stdout.write(polystr(content) + "\n")
                # Ideally this would be in Git canonical even with tags.
                # This is tricky; see reposurgeon's rules for branch coloring.
                # It's not really worth the extra complexity as long at these
                # streams round-trip properly.
                branch = item.branch
                if (
                    (not branch)
                    or (branch not in metadata.symbols)
                    or (not backend.isbranch(metadata.symbols[branch]))
                ):
                    branch = metadata.tipbranch
                if branch == "trunk":
                    branch = "master"
                oldbranch = branch
                for c in "~^\\*?":
                    branch = branch.replace(c, "")
                if not branch:
                    croak("branch name %s is ill-formed" % oldbranch)
                elif branch != oldbranch:
                    announce("branch name %s sanitized to %s" % (oldbranch, branch))
                ref_prefix = "refs/heads/"
                ref_name = branch
                ref_key = branch
                if primary_tag and item.revno == ctx.lo:
                    ref_prefix = "refs/tags/"
                    ref_name = primary_tag
                    ref_key = "refs/tags/" + primary_tag
                    tips.setdefault(branch, 0)
                if ref_key not in tips:
                    sys.stdout.write("reset %s%s\n" % (ref_prefix, ref_name))
                sys.stdout.write("commit %s%s\n" % (ref_prefix, ref_name))
                # Hidden magic for cluing in reposurgeon
                if "--reposurgeon" in args:
                    oid = item.revno
                    if repodir != ".src":
                        oid = item.native
                    sys.stdout.write("#legacy-id %s\n" % oid)
                sys.stdout.write("mark :%d\n" % (mark + 1))
                sys.stdout.write(attribute(item, "author", attribution))
                sys.stdout.write(attribute(item, "committer", attribution))
                sys.stdout.write("data %s\n%s" % (len(item.log), item.log))
                if last_commit_mark:
                    sys.stdout.write("from :%d\n" % last_commit_mark)
                arg = xc.pathbase
                if arg == ".srcignore":
                    arg = ".gitignore"
                arg = fi_quote(arg)
                sys.stdout.write("M %s :%d %s\n\n" % (perms, mark, arg))
                mark += 1
                last_commit_mark = mark
                markmap[item.revno] = mark
                tips[branch] = mark
                if item.revno in tagmap:
                    for key in tagmap[item.revno]:
                        sys.stdout.write(
                            "reset refs/tags/%s\nfrom :%d\n\n"
                            % (key, markmap[item.revno])
                        )
    # At some point git-fast-export stopped issuing branch-tip resets.
    # for branch in tips:
    #    sys.stdout.write("reset refs/heads/%s\nfrom :%d\n\n" % (branch, tips[branch]))


def fast_import_method(*args: str) -> None:
    "Accept a git fast-import stream on stdin, turn it into file histories."
    if not isinstance(backend, RCS):
        croak("fast-import is only supported with the RCS backend")
    if os.path.exists("RCS"):
        croak("refusing to unpack into existing RCS directory!")
    # Force -l to fit SRC's lockless interface.
    command = r"rcs-fast-import -l"
    if args:
        command += " " + " ".join(shlex.quote(arg) for arg in args)
    do_or_die(command, "fast_import_method", missing="rcs-fast-import")
    try:
        os.makedirs(repodir)
    except OSError:
        pass
    for fn in os.listdir("RCS"):
        corresponding = os.path.join("RCS", os.path.basename(fn))
        fn = os.path.join(repodir, os.path.basename(fn))
        if os.path.exists(fn):
            croak("%s exists, aborting leaving RCS in place!" % corresponding)
        rename(corresponding, fn, "fast-import")
    shutil.rmtree("RCS")


# pylint: disable=unused-argument
def version_method(*args: str) -> None:
    "Report SRC's version"
    sys.stdout.write("src: %s\n" % version)
    (major, minor, micro, _releaselevel, _serial) = sys.version_info
    sys.stdout.write("python: %s.%s.%s\n" % (major, minor, micro))
    sys.stdout.write("%s: %s\n" % (backend.__class__.__name__, backend.version()))
    sys.stdout.write("platform: %s\n" % sys.platform)
    if os.path.exists(".git"):  # pragma: no cover
        sys.stdout.write(
            "revision: %s\n" % polystr(capture_or_die("git rev-parse HEAD"))
        )


dispatch: dict[str, Callable[..., None]] = {
    "help": help_method,
    "commit": commit_method,
    "ci": commit_method,
    "add": add_method,
    "amend": amend_method,
    "am": amend_method,
    "uncommit": uncommit_method,
    "un": uncommit_method,
    "init": init_method,
    "list": list_method,
    "li": list_method,
    "log": log_method,
    "checkout": checkout_method,
    "co": checkout_method,
    "status": status_method,
    "st": status_method,
    "cat": cat_method,
    "diff": diff_method,
    "di": diff_method,
    "tag": tag_method,
    "branch": branch_method,
    "rn": rename_method,
    "rename": rename_method,
    "ls": ls_method,
    "move": move_method,
    "mv": move_method,
    "copy": copy_method,
    "cp": copy_method,
    "visualize": visualize_method,
    "vis": visualize_method,
    "fast-export": fast_export_method,
    "fast-import": fast_import_method,
    "release": release_method,
    "srcify": srcify_method,
    "version": version_method,
}

# Interpreting branch and revision numbers
#
# SCCS and RCS were originally designed on the assumption that a revision
# within a branch is named by a major and minor release number. The
# terminology used for these parts has varied.  When you check in a change
# without specifying a revision, the minor number is incremented from the one
# on the tip of the current branch and the major number is left unchanged.
#
# RCS conventions are better documented. Examples from
# the GNU RCS manual follow; see
# https://www.gnu.org/software/rcs/manual/rcs.html
# sections 1.2.3 and  3.1.2 for details.
#
# 1.1         -- revision number for initial checkin (typically);
#                branch number: 1
#                next higher branch number:   2
#                next higher revision number: 1.2
#
# 9.4.1.42    -- more complicated (perhaps after much gnarly hacking);
#                branch number: 9.4.1
#                next higher branch number:   9.4.2
#                next higher revision number: 9.4.1.43
#
# 33.333.333  -- not a valid revision number;
#                however, a perfectly valid branch number
#                next higher branch number:   333.333.334
#                next higher revision number: 333.333.333.1
#
# A revision ID may have any (even) number of components. Branches are designated
# by IDs with an odd number of components. Revision and branch numbers never
# contain zero (the manual says "All integers are positive.").
#
# The manual says: "The branch point of a non-trunk branch is the
# revision number formed by removing the branch's trailing integer. To
# compute the next higher branch or revision number, add one to the
# trailing integer. The highest-numbered revision on a branch is
# called the tip of the branch (or branch tip)."
#
# SCCS numbering (not supported yet) works differently from RCS
# numbering.  Details at http://osr507doc.sco.com/en/tools/SCCS_delta_numbering.html
# Unfortunately, he official GNU SCCS documentation at
# https://www.gnu.org/software/cssc/manual/index.html
# has almost nothing useful to say about it.
#
# SCCS node IDs have at most 4 parts in the form R.B.L.S (release, branch,
# level, sequence - slightly different terminology than RCS would later use).
# Branch IDs are distinguished by an explicit trailing zero.
#
# 1.0 - Trunk banch ID
# 1.1 - First checkin on trunk
# 1.1.1.0 - ID of first branch from trunk v1.1
# 1.1.1.1 - Next checkin on that branch
# 1.1.2.0 - Second branch from v1.1
# 1.2 - Next checkin on trunk.
#
# The main difference is that in original AT&T SCCS you could not
# branch from a branch, only from trunk. This restriction was removed
# in at least some later versions, including CSSC and the Schilling
# fork.  In section 3.5.3 the CSSC manual says
#
# "When a branch is created from an existing sid, the release and level
# numbers are copied, the branch number is set to the lowest unused
# value for that release and level, and the sequence number is set to
# one. Hence the first branch from version 1.1 will be version 1.1.1.1,
# and if a branch is made from that, its sid will be 1.1.2.1."
#
# Jorg Schilling writes, 2018-11-29: "I cannot speak for RCS, but the
# naming conventions used for branches in SCCS are not engraved into
# the sources but rather a convention that is encouraged by the way
# "get -e -b" works with or without -rSID option. SCCS internally uses
# serial numbers and for this reason it is currently limited to 2G
# deltas even though the R.B.L.S scheme could allow more. You could
# even edit the p.file and control the SID that is used for the next
# delget(1) as long as you don't violate basic rules."
#
# In both SCCS and RCS, you normally construct branch numbers to pass them
# to the checkin command to make the checkin happen on a new branch.
# The actual ID generated for that revision will be different;
# in RCS it will have a 1 appended, in RCS the trailing 0 will be
# replaced with a 1.
#
# In SCCS, it is documented in one SCO version that passing a branch
# number to a retrieval command will retrieve the branch tip revision.
# This is not documented in Solaris or GNU SCCS.  Nor is it explictly
# documented in GNU RCS, though there are hints in various parts related
# to revision numbers and it actually works there.
#
# Interpreting symbol values
#
# SCCS doesn't have symbols (name-to-revision or name-to-branch
# associations) at all. RCS has them and stores them in a header
# section of the master file.
#
# A weird curveball that RCS tosses is that the values of branch symbols are
# sometimes (always?) stored in masters with a zero inserted as the second
# to last component.  That is, for example, "1.3.1" is stored as "1.3.0.1"
# and even displayed that way in rlog output. I have seen, but cannot find,
# an RCS document that muttered this was an "efficiency hack". SRC never
# had to notice this quirk, as it always refers to branches by name.
#
# The release-numbering problem
#
# In all of the above examples except two deliberately odd ones from the GNU
# manual, the major part of a revision ID is always 1. It is possible to
# change the major part by specifying a revision when you check in, but this
# has seldom actually been done. SRC itself never does this, but it's a
# possibility (if a remote one) in CVS, RCS, and SCCS collections.
#
# This possibility matters when we are trying to find the branch tip
# or base associated with a particular revision. Breaks introduced
# by major-number changes will screw up the traversal.
#
# Note that SRC uses the empty string as the predecessor of the first
# (1.1) revision.


class RevisionMixin:
    "Express common operations on RCS and SCCS revisions."

    @staticmethod
    def splitrev(rev: str) -> list[int]:
        "Native revision to numeric tuple."
        return [int(d) for d in rev.split(".")]

    @staticmethod
    def joinrev(rev: Iterable[object]) -> str:
        "Numeric tuple to native revision."
        return ".".join([str(d) for d in rev])

    def pred(self, rev: str) -> str:
        "Our predecessor. Walks up parent branch."
        # Assumes the release number has never beem bumped.
        n = self.splitrev(rev)
        if n[-1] > 1:
            n[-1] -= 1
            rev = self.joinrev(n)
        else:
            rev = self.joinrev(n[:-2])
        return rev

    def succ(self, rev: str) -> str:
        "Our successor node, in any back end."
        # Assumes the release number is never bumped.
        if rev:
            n = self.splitrev(rev)
            n[-1] += 1
            return self.joinrev(n)
        else:
            return "1.1"

    def branch_to_base(self, revid: str) -> str:
        "Go from a branch ID tag to the first revision of its branch."
        rev = self.branch_to_parent(revid)
        if rev:
            rev += ".1.1"
        else:
            rev = "1.1"
        return rev

    def branch_to_tip(self, revid: str, metadata: History) -> str:
        "Go from a branch ID tag to the tip revision of its branch."
        rev = self.branch_to_base(revid)
        while True:
            nxt = self.succ(rev)
            if metadata.native_to_revno(nxt) is None:
                return rev
            else:
                rev = nxt
        croak("internal error: couldn't find branch tip of %s" % rev)

    def branch_child(self, name: str, revision: str | None, metadata: History) -> str:
        "Compute a base revision for a named branch."
        if name in metadata.symbols:
            return metadata.symbols[name]
        else:

            def branchfrom(parts: list[int], parent: list[int]) -> int | None:
                "Return the sibling number if parts names a child branch."
                if parts[: len(parent)] != parent:
                    return None
                if len(parts) == len(parent) + 1:
                    return parts[-1]
                if len(parts) == len(parent) + 2:
                    return parts[-2]
                return None

            baserev = metadata.current()
            parent = self.splitrev(baserev.native)
            siblings = []
            for rev in metadata.symbols.values():
                if self.isbranch(rev):
                    sibling = branchfrom(self.splitrev(rev), parent)
                    if sibling is not None:
                        siblings.append(sibling)
            for item in metadata.revlist:
                sibling = branchfrom(self.splitrev(item.native), parent)
                if sibling is not None:
                    siblings.append(sibling)
            newsib = max(siblings or [0]) + 1
            base = baserev.native + "." + str(newsib)
            return base


def makerepodir(target: str) -> None:
    "Make a repo subdirectory if it does not exist."
    targetdir = os.path.dirname(target)
    subrepodir = os.path.join(targetdir, repodir)
    if targetdir and not os.path.isdir(subrepodir):
        os.mkdir(subrepodir)


class RCS(RevisionMixin):
    "Encapsulate RCS back end methods."
    delimiters = (
        "----------------------------",
        "=============================================================================",
    )
    has_branches = True
    RCS_SAVE = "RCS-save"
    RCS_LOCK = ".src-lock"

    class RCSManager:
        "Execution context for backend methods."

        def __init__(self, path: str) -> None:
            self.path: str = path
            self.pathbase: str = os.path.basename(path)
            self.__where: str = os.getcwd()
            self.__deferred: list[int] = []
            self.__previous_handlers: dict[int, Any] = {}
            self.__lock: TextIO | None = None

        def defer_signal(
            self, sig_num: int, stack_frame: FrameType | None
        ) -> None:  # pragma: no cover (passed as hook)
            self.__deferred.append(sig_num)

        def __enter__(self) -> RCS.RCSManager:
            # pylint: disable=global-statement
            global repodir, multidir
            # Replace existing signal handlers with deferred handler
            for sig_num in (signal.SIGHUP, signal.SIGINT, signal.SIGTERM):
                # signal.signal returns None when no handler has been
                # set in Python, which is the same as the default
                # handler (SIG_DFL) being set
                self.__previous_handlers[sig_num] = (
                    signal.signal(sig_num, self.defer_signal) or signal.SIG_DFL
                )
            if os.path.dirname(self.path):
                dirname = os.path.dirname(self.path)
                chdir(dirname, "enter from %s" % (caller(2) if debug else None))
            self.__lock = io.open(RCS.RCS_LOCK, "a", encoding=master_encoding)
            fcntl.flock(self.__lock.fileno(), fcntl.LOCK_EX)
            if repodir == "RCS" and not forced_repodir and os.path.exists(".src"):
                repodir = ".src"
                multidir = os.path.exists("RCS")
            if not os.path.exists(repodir):
                croak("repository subdirectory %s does not exist" % relative(repodir))
            elif repodir != "RCS" and os.path.exists(repodir):
                if os.path.exists("RCS"):
                    rename("RCS", RCS.RCS_SAVE, "stashing")
                rename(repodir, "RCS", "setting up for RCS")
            return self

        def __exit__(
            self,
            extype: type[BaseException] | None,
            value: BaseException | None,
            traceback_unused: TracebackType | None,
        ) -> bool:
            if repodir != "RCS" and not os.path.exists(repodir):
                rename("RCS", repodir, "restoring")
                if os.path.exists(RCS.RCS_SAVE):
                    rename(RCS.RCS_SAVE, "RCS", "unstashing")
            if self.__lock is not None:
                fcntl.flock(self.__lock.fileno(), fcntl.LOCK_UN)
                self.__lock.close()
                self.__lock = None
            chdir(self.__where, "within %s exit" % (caller(2) if debug else None))
            if extype and debug > 0:
                raise extype(value)
            # Restore handlers
            for sig_num, handler in self.__previous_handlers.items():
                signal.signal(sig_num, handler)
            # Send deferred signals
            while self.__deferred:
                sig_num = self.__deferred.pop(0)
                os.kill(os.getpid(), sig_num)
            return False  # Don't suppress errors

    @staticmethod
    def manager(path: str) -> RCS.RCSManager:
        return RCS.RCSManager(path)

    @staticmethod
    def history(arg: str) -> str:
        "History file corresponding to an RCS workfile."
        # The reason this is required is that we might not be within the
        # manager context when this function is called.  Thus we have to
        # check both possible locations for the master.
        for d in (backend.__class__.__name__, repodir):
            p = os.path.join(os.path.dirname(arg), d, os.path.basename(arg) + ",v")
            if os.path.exists(p):
                return p
        return p  # Use repodir as a default for nonexistent targets

    @staticmethod
    def workfile(arg: str) -> str:
        "Workfile corresponding to an RCS master"
        arg = arg[:-2]
        parts = arg.split(os.path.sep)
        if len(parts) > 1 and repodir in parts:
            parts.remove(repodir)
            arg = os.path.sep.join(parts)
        return arg

    @staticmethod
    def isbranch(revid: str) -> bool:
        "Is this a branch symbol?"
        return (revid.count(".")) % 2 == 0

    def revision_to_branch(self, revid: str) -> str:
        "Go from a revision to its branch."
        return self.joinrev(self.splitrev(revid)[:-1])

    def branch_to_parent(self, revid: str) -> str:
        "Go from a revision or branch ID tag to the revision it was based on."
        remove = 1 if self.isbranch(revid) else 2
        return self.joinrev(self.splitrev(revid)[:-remove])

    @staticmethod
    def is_history(path: str) -> bool:
        return path.endswith(",v")

    def has_revisions(self, arg: str) -> bool:
        "Does the master for this file have any revisions"
        # The magic number 105 is the size of an empty RCS file (no
        # metadata, no revisions) at 76 bytes, plus 29 bytes.  We assume
        # that this size has stayed constant or increased since ancient
        # times.  In fact the size of an RCS file with revisions goes up
        # more - by the 78 bytes for the final, fixed line of the log
        # display.  This gives us plenty of slack to cope with minor
        # format differences.
        #
        # The motivation here is to make "src status" faster by avoiding
        # the need for an entire log parse when checking for "A" status.
        return os.path.getsize(self.history(arg)) > 105

    @staticmethod
    def register(arg: str) -> None:
        "Register a file. *Not* called from a manager context."
        rcs_master = os.path.join("RCS", arg + ",v")
        master = os.path.join(repodir, arg + ",v")
        if repodir != "RCS" and os.path.exists(rcs_master):
            croak("name collision with a pre-existing RCS directory.")
        # repodir could be .src or RCS or something random; cope
        if not os.path.isdir(repodir):
            if debug >= DEBUG_COMMANDS:
                logit("mkdir(%s)\n" % repodir)
            os.mkdir(repodir)
        # Key choices here: -b suppresses all keyword expansion, -U sets
        # non-strict locking (which makes branch appends less painful).
        do_or_die(
            "rcs {1} -U -kb -i {0} </dev/null".format(
                shlex.quote(arg), "" if debug else "-q"
            ),
            caller(1, "register") if debug else None,
        )
        # Depending on whether the RCS directory exists, the master can be
        # created either in the current directory or in the RCS directory.
        # Handle both cases. he move in the second case is safe because
        # we bailed out earlier rather than have a name collision here.
        arg += ",v"
        if os.path.exists(arg):
            rename(arg, master, caller(1, "register A case") if debug else None)
        elif os.path.exists(rcs_master):
            if repodir != "RCS":
                rename(
                    rcs_master, master, caller(1, "register B case") if debug else None
                )
        else:
            croak("failed to create master at %s." % master)  # pragma: no cover

    def checkin(self, arg: str, comment: str) -> None:
        "Check in a commit, with comment."
        # The ci -l option makes the file writeable (and locked) after checkin.
        # By unlocking the file *before* checkin with rcs -u we invoke the
        # following property described on the rcs(1) manual page: "If rev is
        # omitted and the caller has no lock, but owns the file and
        # locking is not set to strict, then the revision is appended to
        # the default branch (normally the trunk; see the -b option of
        # rcs(1))."  This is the behavior we want and why locking is set
        # to non-strict.
        do_or_die(
            "rcs {2} -U -u {0},v && ci -l -m{1} {0}".format(
                shlex.quote(arg), shlex.quote(comment), "" if debug else "-q"
            ),
            caller(1, "checkin") if debug else None,
        )

    def checkout(self, arg: str, revision: str | None) -> None:
        "Check out a revision. Leaves it writeable."
        # The operation sequence is: Remove workfile, remove the current lock,
        # checkout the required revision locked.
        if revision is None:
            revision = ""
        do_or_die(
            "rm -f {0} && rcs {2} -u {0},v && co {2} -l{1} {0}".format(
                shlex.quote(arg), revision, "" if debug else "-q"
            ),
            caller(1, "checkout") if debug else None,
        )

    def amend(self, arg: str, rev: str, comment: str) -> None:
        "Amend a commit comment."
        do_or_die(
            "rcs -m{0}:{1} {2}".format(rev, shlex.quote(comment), shlex.quote(arg)),
            caller(1, "amend") if debug else None,
        )

    def uncommit(self, arg: str, rev: str) -> None:
        "Remove the last commit, leaving the workfile unaltered."
        do_or_die(
            "rcs {2} -u {0},v && rcs {2} -o{1} {0}".format(
                shlex.quote(arg), rev, "" if debug else "-q"
            ),
            caller(1, "uncommit") if debug else None,
        )

    def cat(self, arg: str, revision: str | None) -> popen_or_die:
        "Ship the contents of a revision to stdout or a named file."
        return popen_or_die(
            "co {2} -p -r{1} {0}".format(
                shlex.quote(arg), revision, "" if debug else "-q"
            ),
            caller(1, "cat") if debug else None,
        )

    def delete_tag(self, tagname: str, metadata: History) -> int:
        "Delete a specified tag."
        return do_or_die(
            "rcs -n{0} {1}".format(
                shlex.quote(tagname), shlex.quote(metadata.filename)
            ),
            "",
        )

    def set_tag(self, tagname: str, revision: str | None, metadata: History) -> int:
        "Set a specified tag."
        return do_or_die(
            "rcs -N{0}:{1} {2}".format(
                shlex.quote(tagname), revision, shlex.quote(metadata.filename)
            ),
            caller(1, "set_tag") if debug else None,
        )

    def delete_branch(self, branchname: str, metadata: History) -> int:
        "Delete a specified branch."
        # From rcs(1): -orange deletes ("outdates") the revisions given
        # by range.  A range consisting of a single revision number
        # means that revision.  A range consisting of a branch number
        # means the latest revision on that branch.  A range of the form
        # rev1:rev2 means revisions rev1 to rev2 on the same branch,
        # :rev means from the beginning of the branch containing rev
        # up to and including rev, and rev: means from revision rev to
        # the end of the branch containing rev.  None of the outdated
        # revisions can have branches or locks.
        status = do_or_die(
            "rcs -o{0}:{1} {2}".format(
                self.branch_to_base(metadata.symbols[branchname]),
                self.branch_to_tip(metadata.symbols[branchname], metadata),
                shlex.quote(metadata.filename),
            ),
            caller(1, "delete_branch") if debug else None,
            fatal=False,
        )
        if status != 0:
            return status
        self.delete_tag(branchname, metadata)
        return 0

    def set_branch(self, revision: str, filename: str) -> None:
        "Set the specified branch to be default."
        do_or_die(
            "rcs -b%s %s"
            % (
                revision,
                shlex.quote(filename),
            ),
            caller(1, "set_branch") if debug else None,
        )

    def make_branch(self, name: str, revision: str | None, metadata: History) -> None:
        "Set the specified branch to be default, creating it if required."
        base = self.branch_child(name, revision, metadata)
        # Bind symbol for child branch. Internally, RCS might hack the
        # symbol into the "efficiency hack" form, e.g. 1.3.1 becoming
        # 1.3.0.1, but we don't need to care about that here. Relies
        # on being able to rebind a symbol to the value it currently
        # has without creating a duplicate definition.
        do_or_die(
            "rcs -n{0} {1}".format(
                shlex.quote("%s:%s" % (name, base)), shlex.quote(metadata.filename)
            ),
            caller(1, "make_branch (symbol bind)") if debug else None,
        )
        # Set new default branch
        do_or_die(
            "rcs -b%s %s" % (base, shlex.quote(metadata.filename)),
            caller(1, "make_branch (change default)") if debug else None,
        )

    def move(self, source: str, target: str) -> None:
        "Move a file and its history."
        # Not called under RCSManager
        makerepodir(target)
        do_or_die(
            "mv {0} {1} && mv {2} {3}".format(
                shlex.quote(source),
                shlex.quote(target),
                shlex.quote(self.history(source)),
                shlex.quote(self.history(target)),
            ),
            caller(1, "move") if debug else None,
        )

    def copy(self, source: str, target: str) -> None:
        "Copy a file and its history."
        # Not called under RCSManager
        makerepodir(target)
        do_or_die(
            "cp {0} {1} && cp {2} {3}".format(
                shlex.quote(source),
                shlex.quote(target),
                shlex.quote(self.history(source)),
                shlex.quote(self.history(target)),
            ),
            caller(1, "copy") if debug else None,
        )

    def release(self, arg: str) -> None:
        "Release locks."
        do_or_die(
            "rcs {1} -u {0},v".format(shlex.quote(arg), "" if debug else "-q"),
            caller(1, "release") if debug else None,
        )

    @staticmethod
    def version() -> str | None:
        # rcs --version fails under OS X
        # rcs -V throws an obsolescence warning under GNU RCS 5.9.4
        # We choose the more portable option here.
        rawversion = capture_or_die("rcs -V 2>/dev/null")
        m = re.search(r"[0-9]+\.[0-9]+\.[0-9]+".encode("ascii"), rawversion)
        return m and polystr(m.group(0))

    def parse(self, metadata: History, basename: str) -> None:
        "Get and parse the RCS log output for this file."

        def sortkey(rev: HistoryEntry) -> str:
            return rev.date + ".".join("%010d" % int(n) for n in rev.native.split("."))

        def degrottify(rev: str) -> str:
            # Undo RCS's "efficiency hack" (that's what the manual called it).
            parts = rev.split(".")
            if len(parts) > 3 and parts[-2] == "0":
                parts = parts[:-2] + parts[-1:]
            return self.joinrev(parts)

        metadata.symbols["trunk"] = "1"
        metadata.tipbranch = "trunk"
        with popen_or_die(
            command="cd %s >/dev/null; rlog %s 2>/dev/null; cd ..>/dev/null"
            % (shlex.quote(repodir), shlex.quote(basename)),
            legend=caller(1, "metadata parse") if debug else None,
        ) as fp:
            if debug >= DEBUG_PARSE:
                logit("\t-> init\n")
            state = "init"
            for line in fp:
                line = polystr(line)
                if debug >= DEBUG_PARSE:
                    logit("in: %s\n" % repr(line))
                if state == "init":
                    if line.startswith("locks:"):
                        if debug >= DEBUG_PARSE:
                            logit("\t-> locks\n")
                        state = "locks"
                    elif line.startswith("symbolic names:"):
                        if debug >= DEBUG_PARSE:
                            logit("\t-> symbols\n")
                        state = "symbols"
                    elif line.startswith("branch:"):
                        branch = line.split(":")[1].strip()
                        # Undocumented fact about RCS: The branch "1"
                        # is the same as the blank branch.  Significant
                        # because you can't reset to the blank branch
                        # using rcs -b, that resets to the dynamically
                        # highest branch.
                        if not branch or branch == "1":
                            metadata.tipbranch = "trunk"
                        else:
                            metadata.tipbranch = degrottify(branch)
                    elif line.startswith("description:"):
                        state = "description"
                elif state == "description":
                    if line.startswith("============================"):
                        break
                    elif line.startswith("----------------------------"):
                        if debug >= DEBUG_PARSE:
                            logit("\t-> logheader\n")
                        state = "logheader"
                        metadata.revlist.append(HistoryEntry(metadata))
                        metadata.description = metadata.description[:-1]
                    else:
                        metadata.description += line
                elif state == "locks":
                    if not line[0].isspace():
                        if debug >= DEBUG_PARSE:
                            logit("\t-> init\n")
                        state = "init"
                    else:
                        fields = line.strip().split()
                        metadata.lockrevs.append(fields[1])
                elif state == "symbols":
                    if not line[0].isspace():
                        if debug >= DEBUG_PARSE:
                            logit("\t-> init\n")
                        state = "init"
                    else:
                        fields = line.strip().split()
                        name = fields[0]
                        if name.endswith(":"):
                            name = name[:-1]
                        rev = fields[1]
                        metadata.symbols[name] = degrottify(rev)
                elif state == "logheader":
                    if line.startswith("revision "):
                        fields = line.split()
                        metadata.revlist[-1].native = fields[1]
                    elif line.startswith("----------------------------"):
                        metadata.revlist.append(HistoryEntry(metadata))
                    elif line.startswith("date: "):
                        fields = line.split()
                        date = fields[1] + " " + fields[2]
                        if date.endswith(";"):
                            date = date[:-1]
                        date = date.replace("/", "-").replace(" ", "T") + "Z"
                        metadata.revlist[-1].date = date
                    elif line.startswith("branches:"):
                        continue
                    elif line.startswith("======================="):
                        # This deals with RCS v5.7 issuing a log header
                        # divider just before the terminator, something
                        # v5.8 does not do.
                        if not metadata.revlist[-1].native:
                            metadata.revlist.pop()
                        elif not metadata.revlist[-1].log.endswith("\n"):
                            metadata.revlist[-1].log += "\n"
                        break
                    elif line.strip() == "*** empty log message ***":
                        continue
                    elif metadata.revlist:
                        metadata.revlist[-1].log += line
            # Now that we have the symbol table, set the tip branch by name.
            if metadata.tipbranch != "trunk":
                for k, v in list(metadata.symbols.items()):
                    if v == metadata.tipbranch:
                        metadata.tipbranch = k
                        break
                else:
                    croak("unrecognized branch ID '%s'" % metadata.tipbranch)
            metadata.revlist.sort(key=sortkey)
            for i, item in enumerate(metadata.revlist):
                if pseudotime:
                    # Artificial date one day after the epoch
                    # to avoid timezone issues.
                    item.date = rfc3339(86400 + i * 60)
                item.revno = i + 1
            metadata.revlist.reverse()
            if debug >= DEBUG_PARSE:
                # sys.stdout.write("\t%d revisions\n" % len(metadata.revlist)
                logit("\tlockrevs: %s\n" % metadata.lockrevs)
                logit("\tsymbols: %s\n" % metadata.symbols)
            metadata.build_indices()


class SCCS(RevisionMixin):
    "Encapsulate SCCS back end methods."
    delimiters = ("-X-X-X-X-X--X-X-X-X-X--X-X-X-X-X-",)
    has_branches = False
    SCCS_LOCK = ".sccs-lock"

    class SCCSManager:
        "Execution context for backend methods."

        def __init__(self, path: str) -> None:
            self.path: str = path
            self.pathbase: str = os.path.basename(path)
            self.__where: str = os.getcwd()
            if not os.path.isdir("SCCS"):
                croak("no SCCS directory.")
            self.__deferred: list[int] = []
            self.__previous_handlers: dict[int, Any] = {}
            self.__lock: TextIO | None = None

        def defer_signal(
            self, sig_num: int, stack_frame: FrameType | None
        ) -> None:  # pragma: no cover (passed as hook)
            self.__deferred.append(sig_num)

        def __enter__(self) -> SCCS.SCCSManager:
            # Replace existing signal handlers with deferred handler
            for sig_num in (signal.SIGHUP, signal.SIGINT, signal.SIGTERM):
                # signal.signal returns None when no handler has been
                # set in Python, which is the same as the default
                # handler (SIG_DFL) being set
                self.__previous_handlers[sig_num] = (
                    signal.signal(sig_num, self.defer_signal) or signal.SIG_DFL
                )
            if os.path.dirname(self.path):
                dirname = os.path.dirname(self.path)
                chdir(dirname, "within %s enter" % (caller(2) if debug else None))
            self.__lock = io.open(SCCS.SCCS_LOCK, "a", encoding=master_encoding)
            fcntl.flock(self.__lock.fileno(), fcntl.LOCK_EX)
            if not os.path.exists(repodir):
                croak("repository subdirectory %s does not exist" % relative(repodir))
            return self

        def __exit__(
            self,
            extype: type[BaseException] | None,
            value: BaseException | None,
            traceback_unused: TracebackType | None,
        ) -> bool:
            if self.__lock is not None:
                fcntl.flock(self.__lock.fileno(), fcntl.LOCK_UN)
                self.__lock.close()
                self.__lock = None
            chdir(self.__where, "within %s exit" % (caller(2) if debug else None))
            # Restore handlers
            for sig_num, handler in self.__previous_handlers.items():
                signal.signal(sig_num, handler)
            # Send deferred signals
            while self.__deferred:
                sig_num = self.__deferred.pop(0)
                os.kill(os.getpid(), sig_num)
            return False  # Don't suppress errors

    @staticmethod
    def manager(path: str) -> SCCS.SCCSManager:
        return SCCS.SCCSManager(path)

    @staticmethod
    def __sccsfile(arg: str, pref: str) -> str:
        return os.path.join(
            os.path.dirname(arg), "SCCS", pref + "." + os.path.basename(arg)
        )

    @staticmethod
    def history(arg: str) -> str:
        "History file corresponding to an SCCS workfile."
        return SCCS.__sccsfile(arg, "s")

    @staticmethod
    def workfile(arg: str) -> str:
        "Workfile corresponding to an SCCS master"
        if "SCCS" in arg:
            arg = arg.replace("SCCS/s.", "")
        elif arg.startswith("s."):
            arg = arg[2:]
        return arg

    @staticmethod
    def isbranch(revid: str) -> bool:
        "Is this a branch symbol?"
        return revid.endswith(".0")

    def revision_to_branch(self, revid: str) -> str:
        "Go from a revision to its branch."
        return self.joinrev(self.splitrev(revid)[:-1]) + ".0"

    def branch_to_parent(self, revid: str) -> str:
        "Go from a revisiob or branch ID tag to the revision it was based on."
        return self.joinrev(self.splitrev(revid)[:-2])

    @staticmethod
    def is_history(path: str) -> bool:
        return os.path.basename(path).startswith("s.")

    @staticmethod
    def has_revisions(arg: str) -> bool:
        "Does the master for this file have any revisions"
        # It's not possible to create an SCCS file without at least one
        # revision.
        return True

    @staticmethod
    def register(arg: str) -> None:
        "Register a file"
        if not os.path.isdir("SCCS"):
            os.mkdir("SCCS")

    def checkin(self, arg: str, comment: str) -> None:
        "Check in a commit, with comment."
        if os.path.exists(self.history(arg)):
            cmd = "delta -s -y{1} {0}".format(shlex.quote(arg), shlex.quote(comment))
        else:
            # Yuck - 2>/dev/null is required to banish the message
            # admin: warning: SCCS/XXXXX: No id keywords.
            cmd = "admin -fb -i {0} -y{1} <{0} 2>/dev/null".format(
                shlex.quote(arg), shlex.quote(comment)
            )
        do_or_die("TZ=UTC sccs " + cmd, caller(1, "checkin") if debug else None)
        # After checkin, make it writeable (and locked) again.
        do_or_die(
            "rm -f {0} && sccs get -e -s {0} >/dev/null".format(shlex.quote(arg)),
            caller(1, "get after checkin") if debug else None,
        )

    def checkout(self, arg: str, revision: str | None) -> None:
        "Check out a revision. Leaves it writeable."
        # Do not delete SCCS/p.<file> by hand.  The p-file is SCCS's record of an
        # outstanding edit; removing it directly can leave later operations such as
        # unedit/rmdel observing a state transition that never actually happened.
        # Clear any existing edit through SCCS itself before issuing the new get -e.
        pfile = "SCCS/p." + arg
        if os.path.exists(pfile):
            do_or_die(
                "sccs unedit {0}".format(shlex.quote(arg)),
                caller(1, "checkout (unedit)") if debug else None,
            )
        if revision:
            do_or_die(
                "rm -f {0} && sccs get -s -e -r{1} {0} >/dev/null".format(
                    shlex.quote(arg), revision
                ),
                caller(1, "checkout (revision)") if debug else None,
            )
        else:
            do_or_die(
                "rm -f {0} && sccs get -s -e {0} >/dev/null".format(shlex.quote(arg)),
                caller(1, "checkout (no revision)") if debug else None,
            )

    def amend(self, arg: str, rev: str, comment: str) -> None:
        "Amend a commit comment."
        do_or_die(
            "sccs cdc -r{1} -y{2} {0}".format(
                shlex.quote(arg), rev, shlex.quote(comment)
            ),
            caller(1, "amend") if debug else None,
        )

    def uncommit(self, arg: str, rev: str) -> None:
        "Remove the last commit, leaving the workfile unaltered."
        saved = None
        mode = None
        try:
            # SCCS rmdel refuses to remove a delta if that SID is still present
            # in the p-file as an outstanding edit.  Therefore we must unedit
            # first.  But unedit can overwrite or remove the workfile, so save
            # the current contents and mode, perform unedit+rmdel, then restore
            # the workfile so src uncommit preserves what the user sees.
            if os.path.exists(arg):
                mode = os.stat(arg).st_mode
                with tempfile.NamedTemporaryFile(
                    prefix="src", suffix="tmp", delete=False
                ) as fp:
                    saved = fp.name
                shutil.copyfile(arg, saved)

            pfile = "SCCS/p." + arg
            if os.path.exists(pfile):
                do_or_die(
                    "sccs unedit {0}".format(shlex.quote(arg)),
                    caller(1, "uncommit (unedit)") if debug else None,
                )

            do_or_die(
                "sccs rmdel -r{1} {0}".format(shlex.quote(arg), rev),
                caller(1, "uncommit (rmdel)") if debug else None,
            )

            if saved is not None:
                if os.path.exists(arg):
                    os.chmod(arg, mode | stat.S_IWUSR)
                shutil.copyfile(saved, arg)
                if mode is not None:
                    os.chmod(arg, mode)
        finally:
            if saved is not None and os.path.exists(saved):
                os.unlink(saved)

    def cat(self, arg: str, revision: str | None) -> popen_or_die:
        "Ship the contents of a revision to stdout or a named file."
        if revision:
            return popen_or_die(
                "sccs get -s -p -r{1} {0} 2>/dev/null".format(
                    shlex.quote(arg), revision
                ),
                caller(1, "metadata parse (revision)") if debug else None,
            )
        else:
            return popen_or_die(
                "sccs get -p {0}".format(shlex.quote(arg)),
                caller(1, "metadata parse (no revision)") if debug else None,
            )

    def delete_tag(self, tagname: str, metadata: History) -> NoReturn:
        "Delete a specified tag."
        croak(
            "delete_tag: tags are not supported in the SCCS back end"
        )  # pragma: no cover

    def set_tag(
        self, tagname: str, revision: str | None, metadata: History
    ) -> NoReturn:
        "Set a specified tag."
        croak(
            "set_tag: tags are not supported in the SCCS back end"
        )  # pragma: no cover

    def delete_branch(self, _branchname: str, _metadata: History) -> NoReturn:
        "Delete a specified branch."
        croak(
            "delete_branch: branches are not supported in the SCCS back end"
        )  # pragma: no cover

    def set_branch(self, _revision: str, _filename: str) -> NoReturn:
        "Set the specified branch to be default, creating it if required."
        croak(
            "set_branch: branches are not supported in the SCCS back end"
        )  # pragma: no cover

    def make_branch(
        self, name: str, revision: str | None, metadata: History
    ) -> NoReturn:
        "Set the specified branch to be default, creating it if required."
        croak(
            "make_branch: branches are not supported in the SCCS back end"
        )  # pragma: no cover

    def move(self, source: str, target: str) -> None:
        "Move a file and its history."
        # Not called under SCCSManager
        makerepodir(target)
        do_or_die(
            "mv {0} {1} && mv {2} {3}".format(
                shlex.quote(source),
                shlex.quote(target),
                shlex.quote(self.history(source)),
                shlex.quote(self.history(target)),
            ),
            caller(1, "move") if debug else None,
        )

    def copy(self, source: str, target: str) -> None:
        "Copy a file and its history."
        # Not called under SCCSManager
        makerepodir(target)
        do_or_die(
            "cp {0} {1} && cp {2} {3}".format(
                shlex.quote(source),
                shlex.quote(target),
                shlex.quote(self.history(source)),
                shlex.quote(self.history(target)),
            ),
            caller(1, "copy") if debug else None,
        )

    @staticmethod
    def release(arg: str) -> None:
        "Release locks."
        do_or_die(
            "sccs admin -dla {0}".format(shlex.quote(arg)),
            caller(1, "release") if debug else None,
        )

    @staticmethod
    def version() -> str | None:
        rawversion = capture_or_die("sccs --version 2>&1")
        m = re.search(r"[0-9]+\.[0-9]+\.[0-9]+".encode("ascii"), rawversion)
        return m and polystr(m.group(0))

    def parse(self, metadata: History, basename: str) -> None:
        "Get and parse the SCCS log output for this file."
        metadata.symbols["trunk"] = "1.0"
        with popen_or_die(
            # For `prs -d`, omitting -r selects only the most recently created delta.
            # We need the full delta table, so start at 1.1 and use -l to include that
            # delta and everything created later.
            command="sccs prs -l -r1.1 -d':FD:\n:Dt:\n:C:{1}' {0} 2>/dev/null".format(
                shlex.quote(basename), SCCS.delimiters[0]
            ),
            legend=caller(1, "metadata parse") if debug else None,
        ) as fp:
            if debug >= DEBUG_PARSE:
                logit("\t-> init\n")
            state = "init"
            for line in fp:
                line = polystr(line)
                if debug >= DEBUG_PARSE:
                    logit("in %s: %s\n" % (state, repr(line)))
                if state == "init":
                    if line == "none\n":
                        line = ""
                    metadata.description = line
                    state = "header"
                elif state == "header":
                    comment = ""
                    if line.startswith("D "):
                        try:
                            (_, rev, yymmdd, hhmmss) = line.split()[:4]
                            metadata.revlist.append(HistoryEntry(metadata))
                            metadata.revlist[-1].native = rev
                            yymmdd = yymmdd.replace("/", "-")
                            # In Schilling's SCCS the year has a century part,
                            # in CSSC it does not (yet, as of 2023).  Sun says:
                            #
                            # 'The X/Open standard states that old dates held in
                            # ("yy/mm/dd") format does not change in "s." files, but
                            # the values "yy" which range from 69 - 99 are to be
                            # interpreted as 1969 - 1999 respectively. Values of "yy"
                            # which range from 00 - 68 are to be interpreted as 2000
                            # - 2068 respectively.'
                            #
                            # This disambiguates out to 2068.  Note that on 32-bit
                            # platforms there will be a year-2038 problem sooner
                            # than that.
                            year = yymmdd.split("-")[0]
                            if len(year) < 4:
                                if year <= "68":
                                    yymmdd = str(20) + yymmdd
                                else:
                                    yymmdd = str(19) + yymmdd  # pragma: no cover
                            metadata.revlist[-1].date = yymmdd + "T" + hhmmss + "Z"
                        except ValueError:  # pragma: no cover
                            croak(
                                "ill-formed delta line"
                            )  # pragma: no cover (should never happen)
                        if debug >= DEBUG_PARSE:
                            logit("\t-> header\n")
                        state = "comment"
                elif state == "comment":
                    if line == SCCS.delimiters[0] + "\n":
                        metadata.revlist[-1].log = comment.rstrip() + "\n"
                        if debug >= DEBUG_PARSE:
                            logit("\t-> init\n")
                        state = "header"
                    else:
                        comment += line
            # Feeble attempt to cope if prs output is truncated
            if state == "comment" and metadata.revlist:
                metadata.revlist[-1].log = comment.rstrip() + "\n"
            metadata.revlist.sort(key=lambda x: x.date)
            for i, item in enumerate(metadata.revlist):
                if pseudotime:
                    # Artificial date one day after the epoch
                    # to avoid timezone issues.
                    item.date = rfc3339(86400 + i * 60)
                item.revno = i + 1
            metadata.revlist.reverse()
            try:
                with open(self.__sccsfile(metadata.filename, "p"), "rb") as fp:
                    for line in fp:
                        metadata.lockrevs.append(polystr(line).split()[0])
            except IOError:
                pass
            metadata.build_indices()


backends: tuple[type[RCS], type[SCCS]] = (RCS, SCCS)

if __name__ == "__main__":
    try:
        commandline: list[str] = list(sys.argv[1:])
        repodir = ".src"
        backend = RCS
        multidir = os.path.exists(".src") and os.path.exists("RCS")
        startdir = os.getcwd()

        # If there's no .src directory, use the history
        # directory of whichever back end is active.
        if not os.path.exists(".src"):
            for vcs in backends:
                if os.path.exists(vcs.__name__):
                    repodir = vcs.__name__
                    backend = vcs
                    break

        while commandline and commandline[0].startswith("-"):
            if commandline[0] == "-d":
                debug += 1
            elif commandline[0] == "-q":
                quiet = True
            elif commandline[0] == "-T":
                pseudotime = True
            elif commandline[0] == "-S":
                if len(commandline) < 2:
                    croak("-S requires a following repository directory")
                forced_repodir = True
                repodir = commandline[1]
                commandline.pop(0)
            elif commandline[0] == "-L":
                if len(commandline) < 2:
                    croak("-L requires a following log filename")
                logstream = textopen(commandline[1], "a")
                commandline.pop(0)
            else:
                croak(
                    "unknown option %s before command verb" % commandline[0]
                )  # pragma: no cover
            commandline.pop(0)

        if debug >= DEBUG_COMMANDS:
            logit("Starting at %s\n" % startdir)
            time.sleep(0.1)  # Prevents some kind of weird buffering screwup.

        # User might want to force the back end
        for vcs in backends:
            if commandline and commandline[0] == vcs.__name__.lower():
                backend = vcs
                commandline.pop(0)
                break

        if not commandline:
            help_method()
            raise SystemExit(0)  # pragma: no cover

        # Ugly constraint...
        if backend.__name__ == "SCCS":
            multidir = False
            repodir = "SCCS"
        elif backend.__name__ == "RCS":
            # In theory we could do this check only when .src exists. In practice,
            # we prefer making the program's behavior safer and easier for a human
            # to reason about - in doubtful cases it should just bail out rather than
            # trying to be overly clever.
            if os.path.exists(RCS.RCS_SAVE):
                croak(
                    "%s exists: a previous SRC must have crashed hard." % RCS.RCS_SAVE
                )

        backend = backend()

        if commandline[0] in dispatch:
            dispatch[commandline[0]](*commandline[1:])
        else:
            croak("no such command as '%s'.  Try 'src help'" % commandline[0])
    except KeyboardInterrupt:  # pragma: no cover
        pass

# The following sets edit modes for GNU EMACS
# Local Variables:
# mode:python
# End:
