ensure heads remain unique in topological

Fixed regression where a revision file that contained its own down revision
as a dependency would cause an endless loop in the traversal logic.

Change-Id: Ie8bd3b4d9f81e4bda131ffdbabe7a90c4a715054
Fixes: #843

1 files changed, 10 insertions, 0 deletions

diff --git a/tests/test_revision.py b/tests/test_revision.py
index 31590e3..ef1202a 100644
--- a/tests/test_revision.py
+++ b/tests/test_revision.py
@@ -1347,6 +1347,16 @@ class GraphWithLoopTest(DownIterateTest, InvalidRevisionMapTest):
         )
         self._assert_raises_revision_map_loop(map_, "a")
 
+    def test_revision_dupe_head(self):
+        r1 = Revision("user_foo", None)
+        r2 = Revision("user", "user_foo", dependencies="user_foo")
+
+        self.map = RevisionMap(lambda: [r1, r2])
+
+        self._assert_iteration("heads", None, ["user", "user_foo"])
+
+        eq_(self.map._topological_sort([r1, r2], [r2]), ["user", "user_foo"])
+
     def test_revision_map_no_loop_w_overlapping_substrings(self):
         r1 = Revision("user_foo", None)
         r2 = Revision("user", "user_foo")