hgext/convert/cvsps.py

git: skeleton of a new extension to _directly_ operate on git repos

This is based in part of work I did years ago in hgit, but it's mostly
new code since I'm using pygit2 instead of dulwich and the hg storage
interfaces have improved. Some cleanup of old hgit code by Pulkit,
which I greatly appreciate.

test-git-interop.t does not cover a whole lot of cases, but it
passes. It includes status, diff, making a new commit, and `hg annotate`
working on the git repository.

This is _not_ (yet) production quality code: this is an
experiment. Known technical debt lurking in this implementation:

 * Writing bookmarks just totally ignores transactions.
 * The way progress is threaded down into the gitstore is awful.
 * Ideally we'd find a way to incrementally reindex DAGs. I'm not sure
   how to do that efficiently, so we might need a "known only fast-forwards"
   mode on the DAG indexer for use on `hg commit` and friends.
 * We don't even _try_ to do anything reasonable for `hg pull` or `hg push`.
 * Mercurial need an interface for the changelog type.

Tests currently require git 2.24 as far as I'm aware: `git status` has
some changed output that I didn't try and handle in a compatible way.

This patch has produced some interesting cleanups, most recently on
the manifest type. I expect continuing down this road will produce
other meritorious cleanups throughout our code.

Differential Revision: https://phab.mercurial-scm.org/D6734

# Mercurial built-in replacement for cvsps.
#
# Copyright 2008, Frank Kingswood <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
from __future__ import absolute_import

import functools
import os
import re

from mercurial.i18n import _
from mercurial.pycompat import open
from mercurial import (
    encoding,
    error,
    hook,
    pycompat,
    util,
)
from mercurial.utils import (
    dateutil,
    procutil,
    stringutil,
)

pickle = util.pickle


class logentry(object):
    '''Class logentry has the following attributes:
        .author    - author name as CVS knows it
        .branch    - name of branch this revision is on
        .branches  - revision tuple of branches starting at this revision
        .comment   - commit message
        .commitid  - CVS commitid or None
        .date      - the commit date as a (time, tz) tuple
        .dead      - true if file revision is dead
        .file      - Name of file
        .lines     - a tuple (+lines, -lines) or None
        .parent    - Previous revision of this entry
        .rcs       - name of file as returned from CVS
        .revision  - revision number as tuple
        .tags      - list of tags on the file
        .synthetic - is this a synthetic "file ... added on ..." revision?
        .mergepoint - the branch that has been merged from (if present in
                      rlog output) or None
        .branchpoints - the branches that start at the current entry or empty
    '''

    def __init__(self, **entries):
        self.synthetic = False
        self.__dict__.update(entries)

    def __repr__(self):
        items = ("%s=%r" % (k, self.__dict__[k]) for k in sorted(self.__dict__))
        return "%s(%s)" % (type(self).__name__, ", ".join(items))


class logerror(Exception):
    pass


def getrepopath(cvspath):
    """Return the repository path from a CVS path.

    >>> getrepopath(b'/foo/bar')
    '/foo/bar'
    >>> getrepopath(b'c:/foo/bar')
    '/foo/bar'
    >>> getrepopath(b':pserver:10/foo/bar')
    '/foo/bar'
    >>> getrepopath(b':pserver:10c:/foo/bar')
    '/foo/bar'
    >>> getrepopath(b':pserver:/foo/bar')
    '/foo/bar'
    >>> getrepopath(b':pserver:c:/foo/bar')
    '/foo/bar'
    >>> getrepopath(b':pserver:[e-mail]:/foo/bar')
    '/foo/bar'
    >>> getrepopath(b':pserver:[e-mail]:c:/foo/bar')
    '/foo/bar'
    >>> getrepopath(b'user@server/path/to/repository')
    '/path/to/repository'
    """
    # According to CVS manual, CVS paths are expressed like:
    # [:method:][[user][:password]@]hostname[:[port]]/path/to/repository
    #
    # CVSpath is splitted into parts and then position of the first occurrence
    # of the '/' char after the '@' is located. The solution is the rest of the
    # string after that '/' sign including it

    parts = cvspath.split(b':')
    atposition = parts[-1].find(b'@')
    start = 0

    if atposition != -1:
        start = atposition

    repopath = parts[-1][parts[-1].find(b'/', start) :]
    return repopath


def createlog(ui, directory=None, root=b"", rlog=True, cache=None):
    '''Collect the CVS rlog'''

    # Because we store many duplicate commit log messages, reusing strings
    # saves a lot of memory and pickle storage space.
    _scache = {}

    def scache(s):
        """return a shared version of a string"""
        return _scache.setdefault(s, s)

    ui.status(_(b'collecting CVS rlog\n'))

    log = []  # list of logentry objects containing the CVS state

    # patterns to match in CVS (r)log output, by state of use
    re_00 = re.compile(b'RCS file: (.+)$')
    re_01 = re.compile(b'cvs \\[r?log aborted\\]: (.+)$')
    re_02 = re.compile(b'cvs (r?log|server): (.+)\n$')
    re_03 = re.compile(
        b"(Cannot access.+CVSROOT)|(can't create temporary directory.+)$"
    )
    re_10 = re.compile(b'Working file: (.+)$')
    re_20 = re.compile(b'symbolic names:')
    re_30 = re.compile(b'\t(.+): ([\\d.]+)$')
    re_31 = re.compile(b'----------------------------$')
    re_32 = re.compile(
        b'======================================='
        b'======================================$'
    )
    re_50 = re.compile(br'revision ([\d.]+)(\s+locked by:\s+.+;)?$')
    re_60 = re.compile(
        br'date:\s+(.+);\s+author:\s+(.+);\s+state:\s+(.+?);'
        br'(\s+lines:\s+(\+\d+)?\s+(-\d+)?;)?'
        br'(\s+commitid:\s+([^;]+);)?'
        br'(.*mergepoint:\s+([^;]+);)?'
    )
    re_70 = re.compile(b'branches: (.+);$')

    file_added_re = re.compile(br'file [^/]+ was (initially )?added on branch')

    prefix = b''  # leading path to strip of what we get from CVS

    if directory is None:
        # Current working directory

        # Get the real directory in the repository
        try:
            with open(os.path.join(b'CVS', b'Repository'), b'rb') as f:
                prefix = f.read().strip()
            directory = prefix
            if prefix == b".":
                prefix = b""
        except IOError:
            raise logerror(_(b'not a CVS sandbox'))

        if prefix and not prefix.endswith(pycompat.ossep):
            prefix += pycompat.ossep

        # Use the Root file in the sandbox, if it exists
        try:
            root = open(os.path.join(b'CVS', b'Root'), b'rb').read().strip()
        except IOError:
            pass

    if not root:
        root = encoding.environ.get(b'CVSROOT', b'')

    # read log cache if one exists
    oldlog = []
    date = None

    if cache:
        cachedir = os.path.expanduser(b'~/.hg.cvsps')
        if not os.path.exists(cachedir):
            os.mkdir(cachedir)

        # The cvsps cache pickle needs a uniquified name, based on the
        # repository location. The address may have all sort of nasties
        # in it, slashes, colons and such. So here we take just the
        # alphanumeric characters, concatenated in a way that does not
        # mix up the various components, so that
        #    :pserver:user@server:/path
        # and
        #    /pserver/user/server/path
        # are mapped to different cache file names.
        cachefile = root.split(b":") + [directory, b"cache"]
        cachefile = [b'-'.join(re.findall(br'\w+', s)) for s in cachefile if s]
        cachefile = os.path.join(
            cachedir, b'.'.join([s for s in cachefile if s])
        )

    if cache == b'update':
        try:
            ui.note(_(b'reading cvs log cache %s\n') % cachefile)
            oldlog = pickle.load(open(cachefile, b'rb'))
            for e in oldlog:
                if not (
                    util.safehasattr(e, b'branchpoints')
                    and util.safehasattr(e, b'commitid')
                    and util.safehasattr(e, b'mergepoint')
                ):
                    ui.status(_(b'ignoring old cache\n'))
                    oldlog = []
                    break

            ui.note(_(b'cache has %d log entries\n') % len(oldlog))
        except Exception as e:
            ui.note(_(b'error reading cache: %r\n') % e)

        if oldlog:
            date = oldlog[-1].date  # last commit date as a (time,tz) tuple
            date = dateutil.datestr(date, b'%Y/%m/%d %H:%M:%S %1%2')

    # build the CVS commandline
    cmd = [b'cvs', b'-q']
    if root:
        cmd.append(b'-d%s' % root)
        p = util.normpath(getrepopath(root))
        if not p.endswith(b'/'):
            p += b'/'
        if prefix:
            # looks like normpath replaces "" by "."
            prefix = p + util.normpath(prefix)
        else:
            prefix = p
    cmd.append([b'log', b'rlog'][rlog])
    if date:
        # no space between option and date string
        cmd.append(b'-d>%s' % date)
    cmd.append(directory)

    # state machine begins here
    tags = {}  # dictionary of revisions on current file with their tags
    branchmap = {}  # mapping between branch names and revision numbers
    rcsmap = {}
    state = 0
    store = False  # set when a new record can be appended

    cmd = [procutil.shellquote(arg) for arg in cmd]
    ui.note(_(b"running %s\n") % (b' '.join(cmd)))
    ui.debug(b"prefix=%r directory=%r root=%r\n" % (prefix, directory, root))

    pfp = procutil.popen(b' '.join(cmd), b'rb')
    peek = util.fromnativeeol(pfp.readline())
    while True:
        line = peek
        if line == b'':
            break
        peek = util.fromnativeeol(pfp.readline())
        if line.endswith(b'\n'):
            line = line[:-1]
        # ui.debug('state=%d line=%r\n' % (state, line))

        if state == 0:
            # initial state, consume input until we see 'RCS file'
            match = re_00.match(line)
            if match:
                rcs = match.group(1)
                tags = {}
                if rlog:
                    filename = util.normpath(rcs[:-2])
                    if filename.startswith(prefix):
                        filename = filename[len(prefix) :]
                    if filename.startswith(b'/'):
                        filename = filename[1:]
                    if filename.startswith(b'Attic/'):
                        filename = filename[6:]
                    else:
                        filename = filename.replace(b'/Attic/', b'/')
                    state = 2
                    continue
                state = 1
                continue
            match = re_01.match(line)
            if match:
                raise logerror(match.group(1))
            match = re_02.match(line)
            if match:
                raise logerror(match.group(2))
            if re_03.match(line):
                raise logerror(line)

        elif state == 1:
            # expect 'Working file' (only when using log instead of rlog)
            match = re_10.match(line)
            assert match, _(b'RCS file must be followed by working file')
            filename = util.normpath(match.group(1))
            state = 2

        elif state == 2:
            # expect 'symbolic names'
            if re_20.match(line):
                branchmap = {}
                state = 3

        elif state == 3:
            # read the symbolic names and store as tags
            match = re_30.match(line)
            if match:
                rev = [int(x) for x in match.group(2).split(b'.')]

                # Convert magic branch number to an odd-numbered one
                revn = len(rev)
                if revn > 3 and (revn % 2) == 0 and rev[-2] == 0:
                    rev = rev[:-2] + rev[-1:]
                rev = tuple(rev)

                if rev not in tags:
                    tags[rev] = []
                tags[rev].append(match.group(1))
                branchmap[match.group(1)] = match.group(2)

            elif re_31.match(line):
                state = 5
            elif re_32.match(line):
                state = 0

        elif state == 4:
            # expecting '------' separator before first revision
            if re_31.match(line):
                state = 5
            else:
                assert not re_32.match(line), _(
                    b'must have at least some revisions'
                )

        elif state == 5:
            # expecting revision number and possibly (ignored) lock indication
            # we create the logentry here from values stored in states 0 to 4,
            # as this state is re-entered for subsequent revisions of a file.
            match = re_50.match(line)
            assert match, _(b'expected revision number')
            e = logentry(
                rcs=scache(rcs),
                file=scache(filename),
                revision=tuple([int(x) for x in match.group(1).split(b'.')]),
                branches=[],
                parent=None,
                commitid=None,
                mergepoint=None,
                branchpoints=set(),
            )

            state = 6

        elif state == 6:
            # expecting date, author, state, lines changed
            match = re_60.match(line)
            assert match, _(b'revision must be followed by date line')
            d = match.group(1)
            if d[2] == b'/':
                # Y2K
                d = b'19' + d

            if len(d.split()) != 3:
                # cvs log dates always in GMT
                d = d + b' UTC'
            e.date = dateutil.parsedate(
                d,
                [
                    b'%y/%m/%d %H:%M:%S',
                    b'%Y/%m/%d %H:%M:%S',
                    b'%Y-%m-%d %H:%M:%S',
                ],
            )
            e.author = scache(match.group(2))
            e.dead = match.group(3).lower() == b'dead'

            if match.group(5):
                if match.group(6):
                    e.lines = (int(match.group(5)), int(match.group(6)))
                else:
                    e.lines = (int(match.group(5)), 0)
            elif match.group(6):
                e.lines = (0, int(match.group(6)))
            else:
                e.lines = None

            if match.group(7):  # cvs 1.12 commitid
                e.commitid = match.group(8)

            if match.group(9):  # cvsnt mergepoint
                myrev = match.group(10).split(b'.')
                if len(myrev) == 2:  # head
                    e.mergepoint = b'HEAD'
                else:
                    myrev = b'.'.join(myrev[:-2] + [b'0', myrev[-2]])
                    branches = [b for b in branchmap if branchmap[b] == myrev]
                    assert len(branches) == 1, (
                        b'unknown branch: %s' % e.mergepoint
                    )
                    e.mergepoint = branches[0]

            e.comment = []
            state = 7

        elif state == 7:
            # read the revision numbers of branches that start at this revision
            # or store the commit log message otherwise
            m = re_70.match(line)
            if m:
                e.branches = [
                    tuple([int(y) for y in x.strip().split(b'.')])
                    for x in m.group(1).split(b';')
                ]
                state = 8
            elif re_31.match(line) and re_50.match(peek):
                state = 5
                store = True
            elif re_32.match(line):
                state = 0
                store = True
            else:
                e.comment.append(line)

        elif state == 8:
            # store commit log message
            if re_31.match(line):
                cpeek = peek
                if cpeek.endswith(b'\n'):
                    cpeek = cpeek[:-1]
                if re_50.match(cpeek):
                    state = 5
                    store = True
                else:
                    e.comment.append(line)
            elif re_32.match(line):
                state = 0
                store = True
            else:
                e.comment.append(line)

        # When a file is added on a branch B1, CVS creates a synthetic
        # dead trunk revision 1.1 so that the branch has a root.
        # Likewise, if you merge such a file to a later branch B2 (one
        # that already existed when the file was added on B1), CVS
        # creates a synthetic dead revision 1.1.x.1 on B2.  Don't drop
        # these revisions now, but mark them synthetic so
        # createchangeset() can take care of them.
        if (
            store
            and e.dead
            and e.revision[-1] == 1
            and len(e.comment) == 1  # 1.1 or 1.1.x.1
            and file_added_re.match(e.comment[0])
        ):
            ui.debug(
                b'found synthetic revision in %s: %r\n' % (e.rcs, e.comment[0])
            )
            e.synthetic = True

        if store:
            # clean up the results and save in the log.
            store = False
            e.tags = sorted([scache(x) for x in tags.get(e.revision, [])])
            e.comment = scache(b'\n'.join(e.comment))

            revn = len(e.revision)
            if revn > 3 and (revn % 2) == 0:
                e.branch = tags.get(e.revision[:-1], [None])[0]
            else:
                e.branch = None

            # find the branches starting from this revision
            branchpoints = set()
            for branch, revision in pycompat.iteritems(branchmap):
                revparts = tuple([int(i) for i in revision.split(b'.')])
                if len(revparts) < 2:  # bad tags
                    continue
                if revparts[-2] == 0 and revparts[-1] % 2 == 0:
                    # normal branch
                    if revparts[:-2] == e.revision:
                        branchpoints.add(branch)
                elif revparts == (1, 1, 1):  # vendor branch
                    if revparts in e.branches:
                        branchpoints.add(branch)
            e.branchpoints = branchpoints

            log.append(e)

            rcsmap[e.rcs.replace(b'/Attic/', b'/')] = e.rcs

            if len(log) % 100 == 0:
                ui.status(
                    stringutil.ellipsis(b'%d %s' % (len(log), e.file), 80)
                    + b'\n'
                )

    log.sort(key=lambda x: (x.rcs, x.revision))

    # find parent revisions of individual files
    versions = {}
    for e in sorted(oldlog, key=lambda x: (x.rcs, x.revision)):
        rcs = e.rcs.replace(b'/Attic/', b'/')
        if rcs in rcsmap:
            e.rcs = rcsmap[rcs]
        branch = e.revision[:-1]
        versions[(e.rcs, branch)] = e.revision

    for e in log:
        branch = e.revision[:-1]
        p = versions.get((e.rcs, branch), None)
        if p is None:
            p = e.revision[:-2]
        e.parent = p
        versions[(e.rcs, branch)] = e.revision

    # update the log cache
    if cache:
        if log:
            # join up the old and new logs
            log.sort(key=lambda x: x.date)

            if oldlog and oldlog[-1].date >= log[0].date:
                raise logerror(
                    _(
                        b'log cache overlaps with new log entries,'
                        b' re-run without cache.'
                    )
                )

            log = oldlog + log

            # write the new cachefile
            ui.note(_(b'writing cvs log cache %s\n') % cachefile)
            pickle.dump(log, open(cachefile, b'wb'))
        else:
            log = oldlog

    ui.status(_(b'%d log entries\n') % len(log))

    encodings = ui.configlist(b'convert', b'cvsps.logencoding')
    if encodings:

        def revstr(r):
            # this is needed, because logentry.revision is a tuple of "int"
            # (e.g. (1, 2) for "1.2")
            return b'.'.join(pycompat.maplist(pycompat.bytestr, r))

        for entry in log:
            comment = entry.comment
            for e in encodings:
                try:
                    entry.comment = comment.decode(pycompat.sysstr(e)).encode(
                        'utf-8'
                    )
                    if ui.debugflag:
                        ui.debug(
                            b"transcoding by %s: %s of %s\n"
                            % (e, revstr(entry.revision), entry.file)
                        )
                    break
                except UnicodeDecodeError:
                    pass  # try next encoding
                except LookupError as inst:  # unknown encoding, maybe
                    raise error.Abort(
                        inst,
                        hint=_(
                            b'check convert.cvsps.logencoding configuration'
                        ),
                    )
            else:
                raise error.Abort(
                    _(
                        b"no encoding can transcode"
                        b" CVS log message for %s of %s"
                    )
                    % (revstr(entry.revision), entry.file),
                    hint=_(b'check convert.cvsps.logencoding configuration'),
                )

    hook.hook(ui, None, b"cvslog", True, log=log)

    return log


class changeset(object):
    '''Class changeset has the following attributes:
        .id        - integer identifying this changeset (list index)
        .author    - author name as CVS knows it
        .branch    - name of branch this changeset is on, or None
        .comment   - commit message
        .commitid  - CVS commitid or None
        .date      - the commit date as a (time,tz) tuple
        .entries   - list of logentry objects in this changeset
        .parents   - list of one or two parent changesets
        .tags      - list of tags on this changeset
        .synthetic - from synthetic revision "file ... added on branch ..."
        .mergepoint- the branch that has been merged from or None
        .branchpoints- the branches that start at the current entry or empty
    '''

    def __init__(self, **entries):
        self.id = None
        self.synthetic = False
        self.__dict__.update(entries)

    def __repr__(self):
        items = (
            b"%s=%r" % (k, self.__dict__[k]) for k in sorted(self.__dict__)
        )
        return b"%s(%s)" % (type(self).__name__, b", ".join(items))


def createchangeset(ui, log, fuzz=60, mergefrom=None, mergeto=None):
    '''Convert log into changesets.'''

    ui.status(_(b'creating changesets\n'))

    # try to order commitids by date
    mindate = {}
    for e in log:
        if e.commitid:
            if e.commitid not in mindate:
                mindate[e.commitid] = e.date
            else:
                mindate[e.commitid] = min(e.date, mindate[e.commitid])

    # Merge changesets
    log.sort(
        key=lambda x: (
            mindate.get(x.commitid, (-1, 0)),
            x.commitid or b'',
            x.comment,
            x.author,
            x.branch or b'',
            x.date,
            x.branchpoints,
        )
    )

    changesets = []
    files = set()
    c = None
    for i, e in enumerate(log):

        # Check if log entry belongs to the current changeset or not.

        # Since CVS is file-centric, two different file revisions with
        # different branchpoints should be treated as belonging to two
        # different changesets (and the ordering is important and not
        # honoured by cvsps at this point).
        #
        # Consider the following case:
        # foo 1.1 branchpoints: [MYBRANCH]
        # bar 1.1 branchpoints: [MYBRANCH, MYBRANCH2]
        #
        # Here foo is part only of MYBRANCH, but not MYBRANCH2, e.g. a
        # later version of foo may be in MYBRANCH2, so foo should be the
        # first changeset and bar the next and MYBRANCH and MYBRANCH2
        # should both start off of the bar changeset. No provisions are
        # made to ensure that this is, in fact, what happens.
        if not (
            c
            and e.branchpoints == c.branchpoints
            and (  # cvs commitids
                (e.commitid is not None and e.commitid == c.commitid)
                or (  # no commitids, use fuzzy commit detection
                    (e.commitid is None or c.commitid is None)
                    and e.comment == c.comment
                    and e.author == c.author
                    and e.branch == c.branch
                    and (
                        (c.date[0] + c.date[1])
                        <= (e.date[0] + e.date[1])
                        <= (c.date[0] + c.date[1]) + fuzz
                    )
                    and e.file not in files
                )
            )
        ):
            c = changeset(
                comment=e.comment,
                author=e.author,
                branch=e.branch,
                date=e.date,
                entries=[],
                mergepoint=e.mergepoint,
                branchpoints=e.branchpoints,
                commitid=e.commitid,
            )
            changesets.append(c)

            files = set()
            if len(changesets) % 100 == 0:
                t = b'%d %s' % (len(changesets), repr(e.comment)[1:-1])
                ui.status(stringutil.ellipsis(t, 80) + b'\n')

        c.entries.append(e)
        files.add(e.file)
        c.date = e.date  # changeset date is date of latest commit in it

    # Mark synthetic changesets

    for c in changesets:
        # Synthetic revisions always get their own changeset, because
        # the log message includes the filename.  E.g. if you add file3
        # and file4 on a branch, you get four log entries and three
        # changesets:
        #   "File file3 was added on branch ..." (synthetic, 1 entry)
        #   "File file4 was added on branch ..." (synthetic, 1 entry)
        #   "Add file3 and file4 to fix ..."     (real, 2 entries)
        # Hence the check for 1 entry here.
        c.synthetic = len(c.entries) == 1 and c.entries[0].synthetic

    # Sort files in each changeset

    def entitycompare(l, r):
        """Mimic cvsps sorting order"""
        l = l.file.split(b'/')
        r = r.file.split(b'/')
        nl = len(l)
        nr = len(r)
        n = min(nl, nr)
        for i in range(n):
            if i + 1 == nl and nl < nr:
                return -1
            elif i + 1 == nr and nl > nr:
                return +1
            elif l[i] < r[i]:
                return -1
            elif l[i] > r[i]:
                return +1
        return 0

    for c in changesets:
        c.entries.sort(key=functools.cmp_to_key(entitycompare))

    # Sort changesets by date

    odd = set()

    def cscmp(l, r):
        d = sum(l.date) - sum(r.date)
        if d:
            return d

        # detect vendor branches and initial commits on a branch
        le = {}
        for e in l.entries:
            le[e.rcs] = e.revision
        re = {}
        for e in r.entries:
            re[e.rcs] = e.revision

        d = 0
        for e in l.entries:
            if re.get(e.rcs, None) == e.parent:
                assert not d
                d = 1
                break

        for e in r.entries:
            if le.get(e.rcs, None) == e.parent:
                if d:
                    odd.add((l, r))
                d = -1
                break
        # By this point, the changesets are sufficiently compared that
        # we don't really care about ordering. However, this leaves
        # some race conditions in the tests, so we compare on the
        # number of files modified, the files contained in each
        # changeset, and the branchpoints in the change to ensure test
        # output remains stable.

        # recommended replacement for cmp from
        # https://docs.python.org/3.0/whatsnew/3.0.html
        c = lambda x, y: (x > y) - (x < y)
        # Sort bigger changes first.
        if not d:
            d = c(len(l.entries), len(r.entries))
        # Try sorting by filename in the change.
        if not d:
            d = c([e.file for e in l.entries], [e.file for e in r.entries])
        # Try and put changes without a branch point before ones with
        # a branch point.
        if not d:
            d = c(len(l.branchpoints), len(r.branchpoints))
        return d

    changesets.sort(key=functools.cmp_to_key(cscmp))

    # Collect tags

    globaltags = {}
    for c in changesets:
        for e in c.entries:
            for tag in e.tags:
                # remember which is the latest changeset to have this tag
                globaltags[tag] = c

    for c in changesets:
        tags = set()
        for e in c.entries:
            tags.update(e.tags)
        # remember tags only if this is the latest changeset to have it
        c.tags = sorted(tag for tag in tags if globaltags[tag] is c)

    # Find parent changesets, handle {{mergetobranch BRANCHNAME}}
    # by inserting dummy changesets with two parents, and handle
    # {{mergefrombranch BRANCHNAME}} by setting two parents.

    if mergeto is None:
        mergeto = br'{{mergetobranch ([-\w]+)}}'
    if mergeto:
        mergeto = re.compile(mergeto)

    if mergefrom is None:
        mergefrom = br'{{mergefrombranch ([-\w]+)}}'
    if mergefrom:
        mergefrom = re.compile(mergefrom)

    versions = {}  # changeset index where we saw any particular file version
    branches = {}  # changeset index where we saw a branch
    n = len(changesets)
    i = 0
    while i < n:
        c = changesets[i]

        for f in c.entries:
            versions[(f.rcs, f.revision)] = i

        p = None
        if c.branch in branches:
            p = branches[c.branch]
        else:
            # first changeset on a new branch
            # the parent is a changeset with the branch in its
            # branchpoints such that it is the latest possible
            # commit without any intervening, unrelated commits.

            for candidate in pycompat.xrange(i):
                if c.branch not in changesets[candidate].branchpoints:
                    if p is not None:
                        break
                    continue
                p = candidate

        c.parents = []
        if p is not None:
            p = changesets[p]

            # Ensure no changeset has a synthetic changeset as a parent.
            while p.synthetic:
                assert len(p.parents) <= 1, _(
                    b'synthetic changeset cannot have multiple parents'
                )
                if p.parents:
                    p = p.parents[0]
                else:
                    p = None
                    break

            if p is not None:
                c.parents.append(p)

        if c.mergepoint:
            if c.mergepoint == b'HEAD':
                c.mergepoint = None
            c.parents.append(changesets[branches[c.mergepoint]])

        if mergefrom:
            m = mergefrom.search(c.comment)
            if m:
                m = m.group(1)
                if m == b'HEAD':
                    m = None
                try:
                    candidate = changesets[branches[m]]
                except KeyError:
                    ui.warn(
                        _(
                            b"warning: CVS commit message references "
                            b"non-existent branch %r:\n%s\n"
                        )
                        % (pycompat.bytestr(m), c.comment)
                    )
                if m in branches and c.branch != m and not candidate.synthetic:
                    c.parents.append(candidate)

        if mergeto:
            m = mergeto.search(c.comment)
            if m:
                if m.groups():
                    m = m.group(1)
                    if m == b'HEAD':
                        m = None
                else:
                    m = None  # if no group found then merge to HEAD
                if m in branches and c.branch != m:
                    # insert empty changeset for merge
                    cc = changeset(
                        author=c.author,
                        branch=m,
                        date=c.date,
                        comment=b'convert-repo: CVS merge from branch %s'
                        % c.branch,
                        entries=[],
                        tags=[],
                        parents=[changesets[branches[m]], c],
                    )
                    changesets.insert(i + 1, cc)
                    branches[m] = i + 1

                    # adjust our loop counters now we have inserted a new entry
                    n += 1
                    i += 2
                    continue

        branches[c.branch] = i
        i += 1

    # Drop synthetic changesets (safe now that we have ensured no other
    # changesets can have them as parents).
    i = 0
    while i < len(changesets):
        if changesets[i].synthetic:
            del changesets[i]
        else:
            i += 1

    # Number changesets

    for i, c in enumerate(changesets):
        c.id = i + 1

    if odd:
        for l, r in odd:
            if l.id is not None and r.id is not None:
                ui.warn(
                    _(b'changeset %d is both before and after %d\n')
                    % (l.id, r.id)
                )

    ui.status(_(b'%d changeset entries\n') % len(changesets))

    hook.hook(ui, None, b"cvschangesets", True, changesets=changesets)

    return changesets


def debugcvsps(ui, *args, **opts):
    '''Read CVS rlog for current directory or named path in
    repository, and convert the log to changesets based on matching
    commit log entries and dates.
    '''
    opts = pycompat.byteskwargs(opts)
    if opts[b"new_cache"]:
        cache = b"write"
    elif opts[b"update_cache"]:
        cache = b"update"
    else:
        cache = None

    revisions = opts[b"revisions"]

    try:
        if args:
            log = []
            for d in args:
                log += createlog(ui, d, root=opts[b"root"], cache=cache)
        else:
            log = createlog(ui, root=opts[b"root"], cache=cache)
    except logerror as e:
        ui.write(b"%r\n" % e)
        return

    changesets = createchangeset(ui, log, opts[b"fuzz"])
    del log

    # Print changesets (optionally filtered)

    off = len(revisions)
    branches = {}  # latest version number in each branch
    ancestors = {}  # parent branch
    for cs in changesets:

        if opts[b"ancestors"]:
            if cs.branch not in branches and cs.parents and cs.parents[0].id:
                ancestors[cs.branch] = (
                    changesets[cs.parents[0].id - 1].branch,
                    cs.parents[0].id,
                )
            branches[cs.branch] = cs.id

        # limit by branches
        if (
            opts[b"branches"]
            and (cs.branch or b'HEAD') not in opts[b"branches"]
        ):
            continue

        if not off:
            # Note: trailing spaces on several lines here are needed to have
            #       bug-for-bug compatibility with cvsps.
            ui.write(b'---------------------\n')
            ui.write((b'PatchSet %d \n' % cs.id))
            ui.write(
                (
                    b'Date: %s\n'
                    % dateutil.datestr(cs.date, b'%Y/%m/%d %H:%M:%S %1%2')
                )
            )
            ui.write((b'Author: %s\n' % cs.author))
            ui.write((b'Branch: %s\n' % (cs.branch or b'HEAD')))
            ui.write(
                (
                    b'Tag%s: %s \n'
                    % (
                        [b'', b's'][len(cs.tags) > 1],
                        b','.join(cs.tags) or b'(none)',
                    )
                )
            )
            if cs.branchpoints:
                ui.writenoi18n(
                    b'Branchpoints: %s \n' % b', '.join(sorted(cs.branchpoints))
                )
            if opts[b"parents"] and cs.parents:
                if len(cs.parents) > 1:
                    ui.write(
                        (
                            b'Parents: %s\n'
                            % (b','.join([(b"%d" % p.id) for p in cs.parents]))
                        )
                    )
                else:
                    ui.write((b'Parent: %d\n' % cs.parents[0].id))

            if opts[b"ancestors"]:
                b = cs.branch
                r = []
                while b:
                    b, c = ancestors[b]
                    r.append(b'%s:%d:%d' % (b or b"HEAD", c, branches[b]))
                if r:
                    ui.write((b'Ancestors: %s\n' % (b','.join(r))))

            ui.writenoi18n(b'Log:\n')
            ui.write(b'%s\n\n' % cs.comment)
            ui.writenoi18n(b'Members: \n')
            for f in cs.entries:
                fn = f.file
                if fn.startswith(opts[b"prefix"]):
                    fn = fn[len(opts[b"prefix"]) :]
                ui.write(
                    b'\t%s:%s->%s%s \n'
                    % (
                        fn,
                        b'.'.join([b"%d" % x for x in f.parent]) or b'INITIAL',
                        b'.'.join([(b"%d" % x) for x in f.revision]),
                        [b'', b'(DEAD)'][f.dead],
                    )
                )
            ui.write(b'\n')

        # have we seen the start tag?
        if revisions and off:
            if revisions[0] == (b"%d" % cs.id) or revisions[0] in cs.tags:
                off = False

        # see if we reached the end tag
        if len(revisions) > 1 and not off:
            if revisions[1] == (b"%d" % cs.id) or revisions[1] in cs.tags:
                break