Merge instead of rebasing upstream changes in `gclient sync` when --merge is given.

gclient_scm.py

Index: gclient_scm.py
diff --git a/gclient_scm.py b/gclient_scm.py
index 7dc0bd8018693859b15529b74ba0fb747973c5fe..5d9dea95d0c01872150daeb7e35563ea371e4369 100644
--- a/gclient_scm.py
+++ b/gclient_scm.py
@@ -469,7 +469,8 @@ class GitWrapper(SCMWrapper):
       if scm.GIT.IsGitSvn(self.checkout_path) and upstream_branch is not None:
         # Our git-svn branch (upstream_branch) is our upstream
         self._AttemptRebase(upstream_branch, files, options,
-                            newbase=revision, printed_path=printed_path)
+                            newbase=revision, printed_path=printed_path,
+                            merge=options.merge)
         printed_path = True
       else:
         # Can't find a merge-base since we don't know our upstream. That makes
@@ -479,12 +480,13 @@ class GitWrapper(SCMWrapper):
         if options.revision or deps_revision:
           upstream_branch = revision
         self._AttemptRebase(upstream_branch, files, options,
-                            printed_path=printed_path)
+                            printed_path=printed_path, merge=options.merge)
         printed_path = True
     elif rev_type == 'hash':
       # case 2
       self._AttemptRebase(upstream_branch, files, options,
-                          newbase=revision, printed_path=printed_path)
+                          newbase=revision, printed_path=printed_path,
+                          merge=options.merge)
       printed_path = True
     elif revision.replace('heads', 'remotes/' + self.remote) != upstream_branch:
       # case 4
@@ -517,13 +519,15 @@ class GitWrapper(SCMWrapper):
           while True:
             try:
               action = ask_for_data(
-                  'Cannot fast-forward merge, attempt to rebase? '
-                  '(y)es / (q)uit / (s)kip : ', options)
+                  'Cannot %s, attempt to rebase? '
+                  '(y)es / (q)uit / (s)kip : ' %
+                      'merge' if options.merge else 'fast-forward merge',

[iannucci, 2013/12/16 21:01:15]

Wouldn't we want to still fast-forward, even if merge was selected? I think you
want to parameterize the rebase portion here, not the f-f-m.

[Bernhard Bauer, 2013/12/16 21:39:03]

With this version (and --merge), we will still try to fast-forward first, but
automatically try to merge if we cannot do that (by virtue of calling `git
merge` without --ff-only), and only offer to rebase if that fails. With your
suggestion, we would never rebase, and ask for confirmation before merging. I'm
not sure if that is really necessary, as merging is easier to undo than
rebasing.

+                  options)
             except ValueError:
               raise gclient_utils.Error('Invalid Character')
             if re.match(r'yes|y', action, re.I):
               self._AttemptRebase(upstream_branch, files, options,
-                                  printed_path=printed_path)
+                                  printed_path=printed_path, merge=False)
               printed_path = True
               break
             elif re.match(r'quit|q', action, re.I):
@@ -880,19 +884,26 @@ class GitWrapper(SCMWrapper):
          'create a new branch for your work.') % (revision, self.remote))
 
   def _AttemptRebase(self, upstream, files, options, newbase=None,
-                     branch=None, printed_path=False):
+                     branch=None, printed_path=False, merge=False):
     """Attempt to rebase onto either upstream or, if specified, newbase."""
     if files is not None:
       files.extend(self._Capture(['diff', upstream, '--name-only']).split())
     revision = upstream
     if newbase:
       revision = newbase
+    action = 'merge' if merge else 'rebase'
     if not printed_path:
-      print('\n_____ %s : Attempting rebase onto %s...' % (
-          self.relpath, revision))
+      print('\n_____ %s : Attempting %s onto %s...' % (
+          action, self.relpath, revision))
       printed_path = True
     else:
-      print('Attempting rebase onto %s...' % revision)
+      print('Attempting %s onto %s...' % (action, revision))
+
+    if merge:
+      merge_output = self._Capture(['merge', revision])
+      if options.verbose:
+        print(merge_output)
+      return
 
     # Build the rebase command here using the args
     # git rebase [options] [--onto <newbase>] <upstream> [<branch>]