subrepo: allow git subrepos to push and merge

(master branch only)

gitsubrepo based on patch from David Soria Parra:
http://bitbucket.org/segv/davids-poor-git-subrepo-attempt/

mercurial/subrepo.py

@@ -678,6 +678,25 b' class gitsubrepo(object):'
         # circumstances
         return self._gitstate()
 
+    def merge(self, state):
+        source, revision, kind = state
+        self._fetch(source, revision)
+        base = self._gitcommand(['merge-base', revision,
+                                 self._state[1]]).strip()
+        if base == revision:
+            self.get(state) # fast forward merge
+        elif base != self._state[1]:
+            self._gitcommand(['merge', '--no-commit', revision])
+
+    def push(self, force):
+        cmd = ['push']
+        if force:
+            cmd.append('--force')
+        # as subrepos have no notion of "where to push to" we
+        # assume origin master. This is git's default
+        self._gitcommand(cmd + ['origin', 'master', '-q'])
+        return True
+
 types = {
     'hg': hgsubrepo,
     'svn': svnsubrepo,

tests/test-subrepo-git.t

@@ -81,3 +81,93 b' update to previous substate'
   path s
    source   ../gitroot
    revision da5f5b1d8ffcf62fb8327bcd3c89a4367a6018e7
+
+make $GITROOT pushable, by replacing it with a clone with nothing checked out
+
+  $ cd ..
+  $ git clone gitroot gitrootbare --bare -q
+  $ rm -rf gitroot
+  $ mv gitrootbare gitroot
+
+clone root, make local change
+
+  $ cd t
+  $ hg clone . ../ta
+  updating to branch default
+  cloning subrepo s
+  3 files updated, 0 files merged, 0 files removed, 0 files unresolved
+
+  $ cd ../ta
+  $ echo ggg >> s/g
+  $ hg commit -m ggg
+  committing subrepository $TESTTMP/ta/s
+  $ hg debugsub
+  path s
+   source   ../gitroot
+   revision 79695940086840c99328513acbe35f90fcd55e57
+
+clone root separately, make different local change
+
+  $ cd ../t
+  $ hg clone . ../tb
+  updating to branch default
+  cloning subrepo s
+  3 files updated, 0 files merged, 0 files removed, 0 files unresolved
+
+  $ cd ../tb/s
+  $ echo f > f
+  $ git add f
+  $ cd ..
+
+  $ hg commit -m f
+  committing subrepository $TESTTMP/tb/s
+  $ hg debugsub
+  path s
+   source   ../gitroot
+   revision aa84837ccfbdfedcdcdeeedc309d73e6eb069edc
+
+user b push changes
+
+  $ hg push
+  pushing to $TESTTMP/t
+  searching for changes
+  adding changesets
+  adding manifests
+  adding file changes
+  added 1 changesets with 1 changes to 1 files
+
+user a pulls, merges, commits
+
+  $ cd ../ta
+  $ hg pull
+  pulling from $TESTTMP/t
+  searching for changes
+  adding changesets
+  adding manifests
+  adding file changes
+  added 1 changesets with 1 changes to 1 files (+1 heads)
+  (run 'hg heads' to see heads, 'hg merge' to merge)
+  $ hg merge
+  Automatic merge went well; stopped before committing as requested
+  pulling subrepo s
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  (branch merge, don't forget to commit)
+  $ cat s/f
+  f
+  $ cat s/g
+  g
+  gg
+  ggg
+  $ hg commit -m 'merge'
+  committing subrepository $TESTTMP/ta/s
+  $ hg debugsub
+  path s
+   source   ../gitroot
+   revision f47b465e1bce645dbf37232a00574aa1546ca8d3
+  $ hg push
+  pushing to $TESTTMP/t
+  searching for changes
+  adding changesets
+  adding manifests
+  adding file changes
+  added 2 changesets with 2 changes to 1 files