From 66ec3928392d09cba6037fc6c665cb1aa02e86e1 Mon Sep 17 00:00:00 2001
From: Richard Maw <richard.maw@gmail.com>
Date: Sat, 30 Aug 2014 22:22:48 +0100
Subject: Use git's remotes to determine unpushed branches

Rather than using `git ls-remote` every time to see if there are changes
at the remote end, use a local cache.

Git already solves this problem with its refs/remotes/$foo branch
namespace, so we can just use that instead.

In addition, the detection of which upstream branch to use has been
improved; it now uses git's notion of which the upstream branch of your
current branch is, which saves effort in the implementation, and allows
the name of the local branch to differ from that of the remote branch.

This now won't notice if the branch you currently have checked out had
commits pushed from another source, but for some use-cases this is
preferable, as the result equivalent to if you had built before the
other push.

It may make sense to further extend this logic to check that the local
branch is not ahead of the remote branch, instead of requiring them to
be equal.
---
 morphlib/buildbranch.py | 17 +++++++----------
 morphlib/gitdir.py      | 16 ++++++++++++++++
 2 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/morphlib/buildbranch.py b/morphlib/buildbranch.py
index 885f5cf8..638350e3 100644
--- a/morphlib/buildbranch.py
+++ b/morphlib/buildbranch.py
@@ -222,17 +222,14 @@ class BuildBranch(object):
 
         '''
         for gd, (build_ref, index) in self._to_push.iteritems():
-            remote = gd.get_remote('origin')
-            head_ref = gd.disambiguate_ref(gd.HEAD)
+            head_ref = gd.HEAD
+            upstream_ref = gd.get_upstream_of_branch(head_ref)
+            if upstream_ref is None:
+                yield gd
+                continue
             head_sha1 = gd.resolve_ref_to_commit(head_ref)
-            pushed_refs = sorted(
-                    (remote_ref
-                     for remote_sha1, remote_ref in remote.ls()
-                     # substring match of refs, since ref may be a tag,
-                     # in which case it would end with ^{}
-                     if remote_sha1 == head_sha1 and head_ref in remote_ref),
-                    key=len)
-            if not pushed_refs:
+            upstream_sha1 = gd.resolve_ref_to_commit(upstream_ref)
+            if head_sha1 != upstream_sha1:
                 yield gd
 
     def push_build_branches(self, push_cb=lambda **kwargs: None):
diff --git a/morphlib/gitdir.py b/morphlib/gitdir.py
index 40ac643f..9fef4f1e 100644
--- a/morphlib/gitdir.py
+++ b/morphlib/gitdir.py
@@ -515,6 +515,22 @@ class GitDirectory(object):
             else:
                 return 'refs/heads/' + ref
 
+    def get_upstream_of_branch(self, branch): # pragma: no cover
+        try:
+            out = morphlib.git.gitcmd(
+                self._runcmd, 'rev-parse', '--abbrev-ref',
+                '%s@{upstream}' % branch).strip()
+            return out
+        except cliapp.AppException as e:
+            emsg = str(e)
+            if 'does not point to a branch' in emsg:
+                # ref wasn't a branch, can't have upstream
+                # treat it the same as no upstream for convenience
+                return None
+            elif 'No upstream configured for branch' in emsg:
+                return None
+            raise
+
     def resolve_ref_to_commit(self, ref):
         return self._rev_parse('%s^{commit}' % ref)
 
-- 
cgit v1.2.1