Add hg-to-git conversion utility.

hg-to-git.py  is able to convert a Mercurial repository into a git one,
and preserves the branches in the process (unlike tailor)

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
	  (for keeping a git repo in sync with a hg one)
	- supports hg branches
	- converts hg tags

Signed-off-by: Stelian Pop <stelian@popies.net>
Signed-off-by: Junio C Hamano <junkio@cox.net>

3 files changed, 262 insertions, 0 deletions

diff --git a/Documentation/git-tools.txt b/Documentation/git-tools.txt
index 6b407f9adf..10653ff898 100644
--- a/Documentation/git-tools.txt
+++ b/Documentation/git-tools.txt
@@ -86,6 +86,14 @@ Foreign SCM interface
    series in git back and forth.
 
 
+   - *hg-to-git* (contrib/)
+
+   hg-to-git converts a Mercurial repository into a git one, and
+   preserves the full branch history in the process. hg-to-git can
+   also be used in an incremental way to keep the git repository
+   in sync with the master Mercurial repository.
+
+
 Others
 ------
 
diff --git a/contrib/hg-to-git/hg-to-git.py b/contrib/hg-to-git/hg-to-git.py
new file mode 100755
index 0000000000..37337ff01f
--- /dev/null
+++ b/contrib/hg-to-git/hg-to-git.py
@@ -0,0 +1,233 @@
+#! /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
diff --git a/contrib/hg-to-git/hg-to-git.txt b/contrib/hg-to-git/hg-to-git.txt
new file mode 100644
index 0000000000..91f8fe6410
--- /dev/null
+++ b/contrib/hg-to-git/hg-to-git.txt
@@ -0,0 +1,21 @@
+hg-to-git.py is able to convert a Mercurial repository into a git one,
+and preserves the branches in the process (unlike tailor)
+
+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
+	  (for keeping a git repo in sync with a hg one)
+        - supports hg branches
+        - converts hg tags
+
+Note that the git repository will be created 'in place' (at the same
+location as the source hg repo). You will have to manually remove the
+'.hg' directory after the conversion.
+
+Also note that the incremental conversion uses 'simple' hg changesets
+identifiers (ordinals, as opposed to SHA-1 ids), and since these ids
+are not stable across different repositories the hg-to-git.py state file
+is forever tied to one hg repository.
+
+Stelian Pop <stelian@popies.net>