Mercurial to git converter.

Hi all,

I switched recently from Mercurial to git for some of my projects, and needed a conversion tool with branch support (unlike tailor). I didn't find any, so I ended up writing my own one.

hg-to-git.py can probably be greatly improved (it's a rather crude
combination of shell and python) but it does already work quite well for
me. Features:
	- supports incremental conversion (keep a git repo in sync with a hg
one)
	- supports hg branches
	- converts hg tags 

Feel free to use it, improve it or even include it in mainline git (like git-svn and friends).

Stelian.

#! /usr/bin/python

""" hg-to-svn.py - A Mercurial to GIT converter

    Copyright (C)2007 Stelian Pop <stelian@popies.net>

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2, or (at your option)
    any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
"""

import os, os.path, sys import tempfile, popen2, pickle, getopt import re

# Maps hg version -> git version hgvers = {} # List of children for each hg revision hgchildren = {} # Current branch for each hg revision hgbranch = {}

#------------------------------------------------------------------------------

def usage():

        print """\
%s: [OPTIONS] <hgprj>

options:
    -s, --gitstate=FILE: name of the state to be saved/read
                         for incrementals

required:
    hgprj:  name of the HG project to import (directory)
""" % sys.argv[0]

#------------------------------------------------------------------------------

def getgitenv(user, date):
    env = ''
    elems = re.compile('(.*?)\s+<(.*)>').match(user)
    if elems:
        env += 'export GIT_AUTHOR_NAME="%s" ;' % elems.group(1)
        env += 'export GIT_COMMITER_NAME="%s" ;' % elems.group(1)
        env += 'export GIT_AUTHOR_EMAIL="%s" ;' % elems.group(2)
        env += 'export GIT_COMMITER_EMAIL="%s" ;' % elems.group(2)
    else:
        env += 'export GIT_AUTHOR_NAME="%s" ;' % user
        env += 'export GIT_COMMITER_NAME="%s" ;' % user
        env += 'export GIT_AUTHOR_EMAIL= ;'
        env += 'export GIT_COMMITER_EMAIL= ;'

    env += 'export GIT_AUTHOR_DATE="%s" ;' % date
    env += 'export GIT_COMMITTER_DATE="%s" ;' % date
    return env

#------------------------------------------------------------------------------

state = ''

try:
    opts, args = getopt.getopt(sys.argv[1:], 's:t:', ['gitstate=', 'tempdir='])
    for o, a in opts:
        if o in ('-s', '--gitstate'):
            state = a
            state = os.path.abspath(state)

    if len(args) != 1:
        raise('params')
except:
    usage()
    sys.exit(1)

hgprj = args[0] os.chdir(hgprj)

if state:
    if os.path.exists(state):
        print 'State does exist, reading'
        f = open(state, 'r')
        hgvers = pickle.load(f)
    else:
        print 'State does not exist, first run'

tip = os.popen('hg tip | head -1 | cut -f 2 -d :').read().strip() print 'tip is', tip

# Calculate the branches
print 'analysing the branches...'
hgchildren["0"] = ()
hgbranch["0"] = "master"
for cset in range(1, int(tip) + 1):
    hgchildren[str(cset)] = ()
    prnts = os.popen('hg log -r %d | grep ^parent: | cut -f 2 -d :' % cset).readlines()
    if len(prnts) > 0:
        parent = prnts[0].strip()
    else:
        parent = str(cset - 1)
    hgchildren[parent] += ( str(cset), )
    if len(prnts) > 1:
        mparent = prnts[1].strip()
        hgchildren[mparent] += ( str(cset), )
    else:
        mparent = None

    if mparent:
        # For merge changesets, take either one, preferably the 'master' branch
        if hgbranch[mparent] == 'master':
            hgbranch[str(cset)] = 'master'
        else:
            hgbranch[str(cset)] = hgbranch[parent]
    else:
        # Normal changesets
        # For first children, take the parent branch, for the others create a new branch
        if hgchildren[parent][0] == str(cset):
            hgbranch[str(cset)] = hgbranch[parent]
        else:
            hgbranch[str(cset)] = "branch-" + str(cset)

if not hgvers.has_key("0"):
    print 'creating repository'
    os.system('git-init-db')

# loop through every hg changeset for cset in range(int(tip) + 1):

    # incremental, already seen
    if hgvers.has_key(str(cset)):
        continue

    # get info
    prnts = os.popen('hg log -r %d | grep ^parent: | cut -f 2 -d :' % cset).readlines()
    if len(prnts) > 0:
        parent = prnts[0].strip()
    else:
        parent = str(cset - 1)
    if len(prnts) > 1:
        mparent = prnts[1].strip()
    else:
        mparent = None

    (fdcomment, filecomment) = tempfile.mkstemp()
    csetcomment = os.popen('hg log -r %d -v | grep -v ^changeset: | grep -v ^parent: | grep -v ^user: | grep -v ^date | grep -v ^files: | grep -v ^description: | grep -v ^tag:' % cset).read().strip()
    os.write(fdcomment, csetcomment)
    os.close(fdcomment)

    date = os.popen('hg log -r %d | grep ^date: | cut -f 2- -d :' % cset).read().strip()

    tag = os.popen('hg log -r %d | grep ^tag: | cut -f 2- -d :' % cset).read().strip()

    user = os.popen('hg log -r %d | grep ^user: | cut -f 2- -d :' % cset).read().strip()

    print '-----------------------------------------'
    print 'cset:', cset
    print 'branch:', hgbranch[str(cset)]
    print 'user:', user
    print 'date:', date
    print 'comment:', csetcomment
    print 'parent:', parent
    if mparent:
        print 'mparent:', mparent
    if tag:
        print 'tag:', tag
    print '-----------------------------------------'

    # checkout the parent if necessary
    if cset != 0:
        if hgbranch[str(cset)] == "branch-" + str(cset):
            print 'creating new branch', hgbranch[str(cset)]
            os.system('git-checkout -b %s %s' % (hgbranch[str(cset)], hgvers[parent]))
        else:
            print 'checking out branch', hgbranch[str(cset)]
            os.system('git-checkout %s' % hgbranch[str(cset)])

    # merge
    if mparent:
        if hgbranch[parent] == hgbranch[str(cset)]:
            otherbranch = hgbranch[mparent]
        else:
            otherbranch = hgbranch[parent]
        print 'merging', otherbranch, 'into', hgbranch[str(cset)]
        os.system(getgitenv(user, date) + 'git-merge --no-commit -s ours "" %s %s' % (hgbranch[str(cset)], otherbranch))

    # remove everything except .git and .hg directories
    os.system('find . \( -path "./.hg" -o -path "./.git" \) -prune -o ! -name "." -print | xargs rm -rf')

    # repopulate with checkouted files
    os.system('hg update -C %d' % cset)

    # add new files
    os.system('git-ls-files -x .hg --others | git-update-index --add --stdin')
    # delete removed files
    os.system('git-ls-files -x .hg --deleted | git-update-index --remove --stdin')

    # commit
    os.system(getgitenv(user, date) + 'git-commit -a -F %s' % filecomment)
    os.unlink(filecomment)

    # tag
    if tag and tag != 'tip':
        os.system(getgitenv(user, date) + 'git-tag %s' % tag)

    # delete branch if not used anymore...
    if mparent and len(hgchildren[str(cset)]):
        print "Deleting unused branch:", otherbranch
        os.system('git-branch -d %s' % otherbranch)

    # retrieve and record the version
    vvv = os.popen('git-show | head -1').read()
    vvv = vvv[vvv.index(' ') + 1 : ].strip()
    print 'record', cset, '->', vvv
    hgvers[str(cset)] = vvv

os.system('git-repack -a -d')

# write the state for incrementals
if state:
    print 'Writing state'
    f = open(state, 'w')
    pickle.dump(hgvers, f)

# vim: et ts=8 sw=4 sts=4