git_config: add support for remote '.'

As a fix for issue #149, this patch add support for the remote '.'
(local).

As an alias for the local repository, remote '.' is lacking a fetch =
config in .git/config.

Without such refspec, repo info --overview is not able to process a
local tracking branch.

v2: Check for name == '.' before checking if merge starts with refs/,
    since the case where it's not is invalid.

Signed-off-by: Yann Droneaud <ydroneaud@opteya.com>
Signed-off-by: Filipe Brandenburger <filbranden@google.com>

Change-Id: I8c8fd8602cd68baecb530301ae41d37d751ec85d

git_config.py

@@ -619,7 +619,7 @@ class Remote(object):
   def ToLocal(self, rev):
     """Convert a remote revision string to something we have locally.
     """
-    if IsId(rev):
+    if self.name == '.' or IsId(rev):
       return rev
 
     if not rev.startswith('refs/'):