Handle unusual case in rebase-update where second rebase attempt works.

Previously we just added an assert here but better
to simply succeed in this case, while outputting
the intial failure message.

BUG=425696

Review URL: https://codereview.chromium.org/667793005

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@292687 0039d316-1c4b-4281-b951-d872f2087c98

git_auto_svn.py

@@ -83,7 +83,6 @@ def main(argv):
   assert svn_repo is not None, 'Unable to find svn repo for %s' % match.group(1)
   print 'Found upstream svn repo %s and path %s' % (svn_repo, svn_path)
 
-  prefix = upstream.rsplit('/')[0]
   set_config('svn-remote.svn.url', svn_repo)
   set_config('svn-remote.svn.fetch',
              '%s:refs/remotes/%s' % (svn_path, upstream))

git_rebase_update.py

@@ -148,14 +148,20 @@ def rebase_branch(branch, parent, start_hash):
         git.squash_current_branch(merge_base=start_hash)
         git.rebase(parent, start_hash, branch)
       else:
+        print "Failed!"
+        print
+
         # rebase and leave in mid-rebase state.
         # This second rebase attempt should always fail in the same
         # way that the first one does.  If it magically succeeds then
         # something very strange has happened.
         second_rebase_ret = git.rebase(parent, start_hash, branch)
-        assert(not second_rebase_ret.success)
-        print "Failed!"
-        print
+        if second_rebase_ret.success: # pragma: no cover
+          print "Second rebase succeeded unexpectedly!"
+          print "Please see: http://crbug.com/425696"
+          print "First rebased failed with:"
+          print rebase_ret.stderr
+        else:
           print "Here's what git-rebase (squashed) had to say:"
           print
           print squash_ret.stdout