Add a fallback to origin/trunk too when the branch is not tracked.

Raise an exception in case an upstream branch can't be found.
Fix an exception that was occuring just before when no upstream is found.

Review URL: http://codereview.chromium.org/1755018

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@46011 0039d316-1c4b-4281-b951-d872f2087c98

scm.py

@@ -218,12 +218,21 @@ class GIT(object):
       # Fall back on trying a git-svn upstream branch.
       if GIT.IsGitSvn(cwd):
         upstream_branch = GIT.GetSVNBranch(cwd)
+      else:
+        # Else, try to guess the origin remote.
+        remote_branches = GIT.Capture(
+            ['branch', '-r'], in_directory=cwd)[0].split()
+        if 'origin/master' in remote_branches:
           # Fall back on origin/master if it exits.
-      elif GIT.Capture(['branch', '-r'], in_directory=cwd
-                      )[0].split().count('origin/master'):
           remote = 'origin'
           upstream_branch = 'refs/heads/master'
+        elif 'origin/trunk' in remote_branches:
+          # Fall back on origin/trunk if it exists. Generally a shared
+          # git-svn clone
+          remote = 'origin'
+          upstream_branch = 'refs/heads/trunk'
         else:
+          # Give up.
           remote = None
           upstream_branch = None
     return remote, upstream_branch
@@ -232,7 +241,7 @@ class GIT(object):
   def GetUpstreamBranch(cwd):
     """Gets the current branch's upstream branch."""
     remote, upstream_branch = GIT.FetchUpstreamTuple(cwd)
-    if remote != '.':
+    if remote != '.' and upstream_branch:
       upstream_branch = upstream_branch.replace('heads', 'remotes/' + remote)
     return upstream_branch
 

trychange.py

@@ -216,9 +216,10 @@ class GIT(SCM):
     if not self.diff_against:
       self.diff_against = scm.GIT.GetUpstreamBranch(self.checkout_root)
       if not self.diff_against:
-        print "Unable to determine default branch to diff against."
-        print "Verify this branch is set up to track another"
-        print "(via the --track argument to \"git checkout -b ...\""
+        raise NoTryServerAccess(
+            "Unable to determine default branch to diff against. "
+            "Verify this branch is set up to track another"
+            "(via the --track argument to \"git checkout -b ...\"")
     logging.info("GIT(%s)" % self.checkout_root)
 
   def ReadRootFile(self, filename):