[meld] Add helper to identify unpushed commits to Git backend

[Kai Willadsen <kaiw src gnome org>]

commit fc72184b1f5c3fee463657bc374fecf0d9cf7d4f
Author: Kai Willadsen <kai willadsen gmail com>
Date:   Thu May 9 05:39:30 2013 +1000

    Add helper to identify unpushed commits to Git backend

 meld/vc/git.py |   19 +++++++++++++++++++
 1 files changed, 19 insertions(+), 0 deletions(-)
---
diff --git a/meld/vc/git.py b/meld/vc/git.py
index a145934..743e226 100644
--- a/meld/vc/git.py
+++ b/meld/vc/git.py
@@ -97,6 +97,25 @@ class Vc(_vc.CachedVc):
 
     # Prototyping VC interface version 2
 
+    def get_commits_to_push(self):
+        proc = _vc.popen([self.CMD, "for-each-ref",
+                          "--format=%(refname:short) %(upstream:short)",
+                          "refs/heads"], cwd=self.location)
+        branch_remotes = proc.read().split("\n")[:-1]
+
+        branch_revisions = {}
+        for line in branch_remotes:
+            try:
+                branch, remote = line.split()
+            except ValueError:
+                continue
+
+            proc = _vc.popen([self.CMD, "rev-list", branch, "^" + remote],
+                             cwd=self.location)
+            revisions = proc.read().split("\n")[:-1]
+            branch_revisions[branch] = revisions
+        return branch_revisions
+
     def get_files_to_commit(self, paths):
         files = []
         for p in paths: