Support getting changes of non-HEAD branches

presubmit_support.py

Index: presubmit_support.py
diff --git a/presubmit_support.py b/presubmit_support.py
index 2b01bc356401cea34d7634b6ab87d3ba120a893b..d8e2c5b79224c487fef697c877c4dcae6cf80264 100755
--- a/presubmit_support.py
+++ b/presubmit_support.py
@@ -508,7 +508,7 @@ class InputApi(object):
 
 class _DiffCache(object):
   """Caches diffs retrieved from a particular SCM."""
-  def __init__(self, upstream=None):
+  def __init__(self, upstream=None, *args, **kwargs):
     """Stores the upstream revision against which all diffs will be computed."""
     self._upstream = upstream
 
@@ -519,8 +519,8 @@ class _DiffCache(object):
 
 class _SvnDiffCache(_DiffCache):
   """DiffCache implementation for subversion."""
-  def __init__(self, *args, **kwargs):
-    super(_SvnDiffCache, self).__init__(*args, **kwargs)
+  def __init__(self, upstream=None, *args, **kwargs):
+    super(_SvnDiffCache, self).__init__(upstream, *args, **kwargs)
     self._diffs_by_file = {}
 
   def GetDiff(self, path, local_root):
@@ -532,20 +532,22 @@ class _SvnDiffCache(_DiffCache):
 
 class _GitDiffCache(_DiffCache):
   """DiffCache implementation for git; gets all file diffs at once."""
-  def __init__(self, upstream):
-    super(_GitDiffCache, self).__init__(upstream=upstream)
+  def __init__(self, upstream=None, *args, **kwargs):
+    super(_GitDiffCache, self).__init__(upstream, *args, **kwargs)
     self._diffs_by_file = None
+    self._local_ref = kwargs.get('local_ref', 'HEAD')
 
   def GetDiff(self, path, local_root):
     if not self._diffs_by_file:
-      # Compute a single diff for all files and parse the output; should
-      # with git this is much faster than computing one diff for each file.
+      # Compute a single diff for all files and parse the output; with git
+      # this is much faster than computing one diff for each file.
       diffs = {}
 
       # Don't specify any filenames below, because there are command line length
       # limits on some platforms and GenerateDiff would fail.
       unified_diff = scm.GIT.GenerateDiff(local_root, files=[], full_move=True,
-                                          branch=self._upstream)
+                                          branch=self._upstream,
+                                          branch_head=self._local_ref)
 
       # This regex matches the path twice, separated by a space. Note that
       # filename itself may contain spaces.
@@ -802,13 +804,14 @@ class Change(object):
 
   def __init__(
       self, name, description, local_root, files, issue, patchset, author,
-      upstream=None):
+      upstream=None, local_ref='HEAD'):
     if files is None:
       files = []
     self._name = name
     # Convert root into an absolute path.
     self._local_root = os.path.abspath(local_root)
     self._upstream = upstream
+    self._local_ref = local_ref
     self.issue = issue
     self.patchset = patchset
     self.author_email = author
@@ -821,7 +824,8 @@ class Change(object):
     assert all(
         (isinstance(f, (list, tuple)) and len(f) == 2) for f in files), files
 
-    diff_cache = self._AFFECTED_FILES.DIFF_CACHE(self._upstream)
+    diff_cache = self._AFFECTED_FILES.DIFF_CACHE(self._upstream,
+                                                 local_ref=self._local_ref)
     self._affected_files = [
         self._AFFECTED_FILES(path, action.strip(), self._local_root, diff_cache)
         for action, path in files