Small cleanups in trychange.py

trychange.py

Index: trychange.py
diff --git a/trychange.py b/trychange.py
index 35a57433fd16455da69fe5ee5f3f310aefa37ade..cbb99a99b00477ea49ffac6dd3d0cc3f83397622 100755
--- a/trychange.py
+++ b/trychange.py
@@ -116,6 +116,7 @@ class SVN(SCM):
 
   def GetBots(self):
     try:
+      # Try to search on the subversion repository for the file.
       import gcl
       return gcl.GetCachedFile('PRESUBMIT.py', use_root=True)
     except ImportError:
@@ -131,7 +132,7 @@ class GIT(SCM):
   def __init__(self, *args, **kwargs):
     SCM.__init__(self, *args, **kwargs)
     self.checkout_root = os.path.abspath(
-        gclient_utils.CheckCall(['git', 'rev-parse', '--show-cdup']).strip())
+        scm.GIT.Capture(['rev-parse', '--show-cdup']).strip())
     if not self.options.diff:
       self.options.diff = self._GenerateDiff()
     if not self.options.name:
@@ -145,13 +146,10 @@ class GIT(SCM):
 
   def _GetPatchName(self):
     """Construct a name for this patch."""
-    # TODO: perhaps include the hash of the current commit, to distinguish
-    # patches?
-    branch = gclient_utils.CheckCall(['git', 'symbolic-ref', 'HEAD']).strip()
-    if not branch.startswith('refs/heads/'):
-      # TODO(maruel): Find a better type.
+    branch_ref = scm.GIT.GetBranchRef(self.checkout_root)
+    branch = scm.GIT.ShortBranchName(branch_ref)
+    if branch == branch_ref:
       raise NoTryServerAccess("Couldn't figure out branch name")
-    branch = branch[len('refs/heads/'):]
     return branch
 
   def GetLocalRoot(self):
@@ -160,6 +158,7 @@ class GIT(SCM):
 
   def GetBots(self):
     try:
+      # A git checkout is always a full checkout.
       return gclient_utils.FileRead(os.path.join(self.checkout_root,
                                                  'PRESUBMIT.py'))
     except (IOError, OSError):