view hgext/fastexport.py @ 45059:79f6f9fa18c1

documentation: add some internals documentation about bid merge

This is an important algorithm that was only documented on the wiki so far.

Some update to the algorithm (and associated doc) is to expected in the future
since the bid merge algorithm is bug-ridden when it comes to file deletion comes
to play.

Differential Revision: https://phab.mercurial-scm.org/D8711

# Copyright 2020 Joerg Sonnenberger <[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.
"""export repositories as git fast-import stream"""

# The format specification for fast-import streams can be found at
# https://git-scm.com/docs/git-fast-import#_input_format

from __future__ import absolute_import
import re

from mercurial.i18n import _
from mercurial.node import hex, nullrev
from mercurial.utils import stringutil
from mercurial import (
    error,
    pycompat,
    registrar,
    scmutil,
)
from .convert import convcmd

# Note for extension authors: ONLY specify testedwith = 'ships-with-hg-core' for
# extensions which SHIP WITH MERCURIAL. Non-mainline extensions should
# be specifying the version(s) of Mercurial they are tested with, or
# leave the attribute unspecified.
testedwith = b"ships-with-hg-core"

cmdtable = {}
command = registrar.command(cmdtable)

GIT_PERSON_PROHIBITED = re.compile(b'[<>\n"]')
GIT_EMAIL_PROHIBITED = re.compile(b"[<> \n]")


def convert_to_git_user(authormap, user, rev):
    mapped_user = authormap.get(user, user)
    user_person = stringutil.person(mapped_user)
    user_email = stringutil.email(mapped_user)
    if GIT_EMAIL_PROHIBITED.match(user_email) or GIT_PERSON_PROHIBITED.match(
        user_person
    ):
        raise error.Abort(
            _(b"Unable to parse user into person and email for revision %s")
            % rev
        )
    if user_person:
        return b'"' + user_person + b'" <' + user_email + b'>'
    else:
        return b"<" + user_email + b">"


def convert_to_git_date(date):
    timestamp, utcoff = date
    tzsign = b"+" if utcoff <= 0 else b"-"
    if utcoff % 60 != 0:
        raise error.Abort(
            _(b"UTC offset in %b is not an integer number of seconds") % (date,)
        )
    utcoff = abs(utcoff) // 60
    tzh = utcoff // 60
    tzmin = utcoff % 60
    return b"%d " % int(timestamp) + tzsign + b"%02d%02d" % (tzh, tzmin)


def convert_to_git_ref(branch):
    # XXX filter/map depending on git restrictions
    return b"refs/heads/" + branch


def write_data(buf, data, skip_newline):
    buf.append(b"data %d\n" % len(data))
    buf.append(data)
    if not skip_newline or data[-1:] != b"\n":
        buf.append(b"\n")


def export_commit(ui, repo, rev, marks, authormap):
    ctx = repo[rev]
    revid = ctx.hex()
    if revid in marks:
        ui.debug(b"warning: revision %s already exported, skipped\n" % revid)
        return
    parents = [p for p in ctx.parents() if p.rev() != nullrev]
    for p in parents:
        if p.hex() not in marks:
            ui.warn(
                _(b"warning: parent %s of %s has not been exported, skipped\n")
                % (p, revid)
            )
            return

    # For all files modified by the commit, check if they have already
    # been exported and otherwise dump the blob with the new mark.
    for fname in ctx.files():
        if fname not in ctx:
            continue
        filectx = ctx.filectx(fname)
        filerev = hex(filectx.filenode())
        if filerev not in marks:
            mark = len(marks) + 1
            marks[filerev] = mark
            data = filectx.data()
            buf = [b"blob\n", b"mark :%d\n" % mark]
            write_data(buf, data, False)
            ui.write(*buf, keepprogressbar=True)
            del buf

    # Assign a mark for the current revision for references by
    # latter merge commits.
    mark = len(marks) + 1
    marks[revid] = mark

    ref = convert_to_git_ref(ctx.branch())
    buf = [
        b"commit %s\n" % ref,
        b"mark :%d\n" % mark,
        b"committer %s %s\n"
        % (
            convert_to_git_user(authormap, ctx.user(), revid),
            convert_to_git_date(ctx.date()),
        ),
    ]
    write_data(buf, ctx.description(), True)
    if parents:
        buf.append(b"from :%d\n" % marks[parents[0].hex()])
    if len(parents) == 2:
        buf.append(b"merge :%d\n" % marks[parents[1].hex()])
        p0ctx = repo[parents[0]]
        files = ctx.manifest().diff(p0ctx.manifest())
    else:
        files = ctx.files()
    filebuf = []
    for fname in files:
        if fname not in ctx:
            filebuf.append((fname, b"D %s\n" % fname))
        else:
            filectx = ctx.filectx(fname)
            filerev = filectx.filenode()
            fileperm = b"755" if filectx.isexec() else b"644"
            changed = b"M %s :%d %s\n" % (fileperm, marks[hex(filerev)], fname)
            filebuf.append((fname, changed))
    filebuf.sort()
    buf.extend(changed for (fname, changed) in filebuf)
    del filebuf
    buf.append(b"\n")
    ui.write(*buf, keepprogressbar=True)
    del buf


isrev = re.compile(b"^[0-9a-f]{40}$")


@command(
    b"fastexport",
    [
        (b"r", b"rev", [], _(b"revisions to export"), _(b"REV")),
        (b"i", b"import-marks", b"", _(b"old marks file to read"), _(b"FILE")),
        (b"e", b"export-marks", b"", _(b"new marks file to write"), _(b"FILE")),
        (
            b"A",
            b"authormap",
            b"",
            _(b"remap usernames using this file"),
            _(b"FILE"),
        ),
    ],
    _(b"[OPTION]... [REV]..."),
    helpcategory=command.CATEGORY_IMPORT_EXPORT,
)
def fastexport(ui, repo, *revs, **opts):
    """export repository as git fast-import stream

    This command lets you dump a repository as a human-readable text stream.
    It can be piped into corresponding import routines like "git fast-import".
    Incremental dumps can be created by using marks files.
    """
    opts = pycompat.byteskwargs(opts)

    revs += tuple(opts.get(b"rev", []))
    if not revs:
        revs = scmutil.revrange(repo, [b":"])
    else:
        revs = scmutil.revrange(repo, revs)
    if not revs:
        raise error.Abort(_(b"no revisions matched"))
    authorfile = opts.get(b"authormap")
    if authorfile:
        authormap = convcmd.readauthormap(ui, authorfile)
    else:
        authormap = {}

    import_marks = opts.get(b"import_marks")
    marks = {}
    if import_marks:
        with open(import_marks, "rb") as import_marks_file:
            for line in import_marks_file:
                line = line.strip()
                if not isrev.match(line) or line in marks:
                    raise error.Abort(_(b"Corrupted marks file"))
                marks[line] = len(marks) + 1

    revs.sort()
    with ui.makeprogress(
        _(b"exporting"), unit=_(b"revisions"), total=len(revs)
    ) as progress:
        for rev in revs:
            export_commit(ui, repo, rev, marks, authormap)
            progress.increment()

    export_marks = opts.get(b"export_marks")
    if export_marks:
        with open(export_marks, "wb") as export_marks_file:
            output_marks = [None] * len(marks)
            for k, v in marks.items():
                output_marks[v - 1] = k
            for k in output_marks:
                export_marks_file.write(k + b"\n")