transport-helper: update ref status after push with export

Also add check_output from python 2.7.

Signed-off-by: Sverre Rabbelier <srabbelier@gmail.com>
Acked-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git_remote_helpers/git/importer.py

@@ -1,7 +1,7 @@
 import os
 import subprocess
 
-from git_remote_helpers.util import check_call
+from git_remote_helpers.util import check_call, check_output
 
 
 class GitImporter(object):
@@ -16,6 +16,18 @@ class GitImporter(object):
 
         self.repo = repo
 
+    def get_refs(self, gitdir):
+        """Returns a dictionary with refs.
+        """
+        args = ["git", "--git-dir=" + gitdir, "for-each-ref", "refs/heads"]
+        lines = check_output(args).strip().split('\n')
+        refs = {}
+        for line in lines:
+            value, name = line.split(' ')
+            name = name.strip('commit\t')
+            refs[name] = value
+        return refs
+
     def do_import(self, base):
         """Imports a fast-import stream to the given directory.
 
@@ -32,9 +44,23 @@ class GitImporter(object):
         if not os.path.exists(dirname):
             os.makedirs(dirname)
 
+        refs_before = self.get_refs(gitdir)
+
         args = ["git", "--git-dir=" + gitdir, "fast-import", "--quiet", "--export-marks=" + path]
 
         if os.path.exists(path):
             args.append("--import-marks=" + path)
 
         check_call(args)
+
+        refs_after = self.get_refs(gitdir)
+
+        changed = {}
+
+        for name, value in refs_after.iteritems():
+            if refs_before.get(name) == value:
+                continue
+
+            changed[name] = value
+
+        return changed