Modify scm.GIT.GetUpstreamBranch to behave like git-cl.

It now defaults to origin/master when no branch is tracked.

TEST=git-try on untracked branch now doesn't result in an empty diff
BUG=none

Review URL: http://codereview.chromium.org/1739021

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@45935 0039d316-1c4b-4281-b951-d872f2087c98

gclient_scm.py

@@ -237,11 +237,11 @@ class GitWrapper(SCMWrapper):
     # 4) current branch based on a remote, switches to a new remote
     #   - exit
 
-    # GetUpstream returns something like 'refs/remotes/origin/master' for a
-    # tracking branch
+    # GetUpstreamBranch returns something like 'refs/remotes/origin/master' for
+    # a tracking branch
     # or 'master' if not a tracking branch (it's based on a specific rev/hash)
     # or it returns None if it couldn't find an upstream
-    upstream_branch = scm.GIT.GetUpstream(self.checkout_path)
+    upstream_branch = scm.GIT.GetUpstreamBranch(self.checkout_path)
     if not upstream_branch or not upstream_branch.startswith('refs/remotes'):
       current_type = "hash"
       logging.debug("Current branch is based off a specific rev and is not "

scm.py

@@ -202,6 +202,7 @@ class GIT(object):
   def FetchUpstreamTuple(cwd):
     """Returns a tuple containg remote and remote ref,
        e.g. 'origin', 'refs/heads/master'
+       Tries to be intelligent and understand git-svn.
     """
     remote = '.'
     branch = GIT.GetBranch(cwd)
@@ -217,10 +218,18 @@ class GIT(object):
       # Fall back on trying a git-svn upstream branch.
       if GIT.IsGitSvn(cwd):
         upstream_branch = GIT.GetSVNBranch(cwd)
+      # 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'
+      else:
+        remote = None
+        upstream_branch = None
     return remote, upstream_branch
 
   @staticmethod
-  def GetUpstream(cwd):
+  def GetUpstreamBranch(cwd):
     """Gets the current branch's upstream branch."""
     remote, upstream_branch = GIT.FetchUpstreamTuple(cwd)
     if remote != '.':
@@ -235,7 +244,7 @@ class GIT(object):
     full_move means that move or copy operations should completely recreate the
     files, usually in the prospect to apply the patch for a try job."""
     if not branch:
-      branch = GIT.GetUpstream(cwd)
+      branch = GIT.GetUpstreamBranch(cwd)
     command = ['diff', '-p', '--no-prefix', branch + "..." + branch_head]
     if not full_move:
       command.append('-C')
@@ -255,7 +264,7 @@ class GIT(object):
   def GetDifferentFiles(cwd, branch=None, branch_head='HEAD'):
     """Returns the list of modified files between two branches."""
     if not branch:
-      branch = GIT.GetUpstream(cwd)
+      branch = GIT.GetUpstreamBranch(cwd)
     command = ['diff', '--name-only', branch + "..." + branch_head]
     return GIT.Capture(command, cwd)[0].splitlines(False)
 

tests/scm_unittest.py

@@ -122,7 +122,8 @@ from :3
         'FetchUpstreamTuple',
         'GenerateDiff', 'GetBranch', 'GetBranchRef', 'GetCheckoutRoot',
         'GetDifferentFiles', 'GetEmail', 'GetPatchName', 'GetSVNBranch',
-        'GetUpstream', 'IsGitSvn', 'RunAndFilterOutput', 'ShortBranchName',
+        'GetUpstreamBranch', 'IsGitSvn', 'RunAndFilterOutput',
+        'ShortBranchName',
     ]
     # If this test fails, you should add the relevant test.
     self.compareMembers(scm.GIT, members)

tests/trychange_unittest.py

@@ -19,8 +19,9 @@ class TryChangeTestsBase(SuperMoxTestBase):
     self.mox.StubOutWithMock(trychange.scm.GIT, 'Capture')
     self.mox.StubOutWithMock(trychange.scm.GIT, 'GenerateDiff')
     self.mox.StubOutWithMock(trychange.scm.GIT, 'GetCheckoutRoot')
-    self.mox.StubOutWithMock(trychange.scm.GIT, 'GetPatchName')
     self.mox.StubOutWithMock(trychange.scm.GIT, 'GetEmail')
+    self.mox.StubOutWithMock(trychange.scm.GIT, 'GetPatchName')
+    self.mox.StubOutWithMock(trychange.scm.GIT, 'GetUpstreamBranch')
     self.mox.StubOutWithMock(trychange.scm.SVN, 'DiffItem')
     self.mox.StubOutWithMock(trychange.scm.SVN, 'GenerateDiff')
     self.mox.StubOutWithMock(trychange.scm.SVN, 'GetCheckoutRoot')
@@ -88,10 +89,11 @@ class GITUnittest(TryChangeTestsBase):
 
   def testBasic(self):
     trychange.scm.GIT.GetCheckoutRoot(self.fake_root).AndReturn(self.fake_root)
+    trychange.scm.GIT.GetUpstreamBranch(self.fake_root).AndReturn('somewhere')
     trychange.scm.GIT.GenerateDiff(self.fake_root,
                                    full_move=True,
                                    files=['foo.txt', 'bar.txt'],
-                                   branch=None).AndReturn('A diff')
+                                   branch='somewhere').AndReturn('A diff')
     trychange.scm.GIT.GetPatchName(self.fake_root).AndReturn('bleh-1233')
     trychange.scm.GIT.GetEmail(self.fake_root).AndReturn('georges@example.com')
     self.mox.ReplayAll()

trychange.py

@@ -213,6 +213,12 @@ class GIT(SCM):
       self.options.name = scm.GIT.GetPatchName(self.checkout_root)
     if not self.options.email:
       self.options.email = scm.GIT.GetEmail(self.checkout_root)
+    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 ...\""
     logging.info("GIT(%s)" % self.checkout_root)
 
   def ReadRootFile(self, filename):