Support getting changes of non-HEAD branches

git_cl.py

Index: git_cl.py
diff --git a/git_cl.py b/git_cl.py
index 2927fd6622c22edb2c01704aed2b752c08170329..9218ebd332b072c00ae48c66eca5f4419312f2fb 100755
--- a/git_cl.py
+++ b/git_cl.py
@@ -828,8 +828,11 @@ def ShortBranchName(branch):
 
 def GetCurrentBranchRef():
   """Returns branch ref (e.g., refs/heads/master) or None."""
-  return RunGit(['symbolic-ref', 'HEAD'],
-                stderr=subprocess2.VOID, error_ok=True).strip() or None
+  ref = RunGit(['symbolic-ref', 'HEAD'],
+               stderr=subprocess2.VOID, error_ok=True).strip() or None
+  if ref and not ref.startswith('refs/heads/'):
+    ref = 'refs/heads/'+ref
+  return ref
 
 
 def GetCurrentBranch():
@@ -1112,7 +1115,7 @@ class Changelist(object):
         self._remote = (remote, 'refs/remotes/%s/%s' % (remote, branch))
     return self._remote
 
-  def GitSanityChecks(self, upstream_git_obj):
+  def GitSanityChecks(self, upstream_git_obj, local_ref='HEAD'):
     """Checks git repo status and ensures diff is from local commits."""
 
     if upstream_git_obj is None:
@@ -1126,8 +1129,8 @@ class Changelist(object):
 
     # Verify the commit we're diffing against is in our current branch.
     upstream_sha = RunGit(['rev-parse', '--verify', upstream_git_obj]).strip()
-    common_ancestor = RunGit(['merge-base', upstream_sha, 'HEAD']).strip()
-    if upstream_sha != common_ancestor:
+    common_anc = RunGit(['merge-base', upstream_sha, local_ref]).strip()
+    if upstream_sha != common_anc:
       print >> sys.stderr, (
           'ERROR: %s is not in the current branch.  You may need to rebase '
           'your tracking branch' % upstream_sha)
@@ -1135,7 +1138,7 @@ class Changelist(object):
 
     # List the commits inside the diff, and verify they are all local.
     commits_in_diff = RunGit(
-        ['rev-list', '^%s' % upstream_sha, 'HEAD']).splitlines()
+        ['rev-list', '^%s' % upstream_sha, local_ref]).splitlines()
     code, remote_branch = RunGitWithCode(['config', 'gitcl.remotebranch'])
     remote_branch = remote_branch.strip()
     if code != 0:
@@ -1258,7 +1261,8 @@ class Changelist(object):
       self.SetPatchset(None)
 
   def GetChange(self, upstream_branch, author):
-    if not self.GitSanityChecks(upstream_branch):
+    local_ref = self.GetBranchRef()
+    if not self.GitSanityChecks(upstream_branch, local_ref):
       DieWithError('\nGit sanity check failure')
 
     root = settings.GetRelativeRoot()
@@ -1267,10 +1271,10 @@ class Changelist(object):
     absroot = os.path.abspath(root)
 
     # We use the sha1 of HEAD as a name of this change.
-    name = RunGitWithCode(['rev-parse', 'HEAD'])[1].strip()
+    name = RunGitWithCode(['rev-parse', local_ref])[1].strip()
     # Need to pass a relative path for msysgit.
     try:
-      files = scm.GIT.CaptureStatus([root], '.', upstream_branch)
+      files = scm.GIT.CaptureStatus([root], '.', upstream_branch, local_ref)
     except subprocess2.CalledProcessError:
       DieWithError(
           ('\nFailed to diff against upstream branch %s\n\n'
@@ -1288,7 +1292,8 @@ class Changelist(object):
       # If the change was never uploaded, use the log messages of all commits
       # up to the branch point, as git cl upload will prefill the description
       # with these log messages.
-      args = ['log', '--pretty=format:%s%n%n%b', '%s...' % (upstream_branch)]
+      args = ['log', '--pretty=format:%s%n%n%b',
+              '%s...%s' % (upstream_branch, local_ref)]
       description = RunGitWithCode(args)[1].strip()
 
     if not author:
@@ -1301,7 +1306,8 @@ class Changelist(object):
         issue,
         patchset,
         author,
-        upstream=upstream_branch)
+        upstream=upstream_branch,
+        local_ref=local_ref)
 
   def UpdateDescription(self, description):
     self.description = description