Follow links during exports

If package is linked, we need to follow the link and export the
linked package instead.

lib/git_exporter.py

@@ -135,7 +135,8 @@ class GitExporter:
         added_commits = False
 
         if tree == None:  # eg. python-M2Crypto errors
-            return
+            # fall-back to linked project
+            return False
         flats = tree.as_flat_list()
         branch_state = {"factory": None, "devel": None}
         left_to_commit = self.check_repo_state(flats, branch_state, "factory")
@@ -186,6 +187,7 @@ class GitExporter:
 
         #if added_commits:
         #    self.git.push(force=True)
+        return True
 
     def run_gc(self):
         self.gc_cnt = self.gc_interval