Rev 2402: Shortcut the common_ancestor code when one tip is in the ancestry of the other. in http://bzr.arbash-meinel.com/branches/bzr/0.16-dev/shortcut-common-ancestor

[John Arbash Meinel]

At http://bzr.arbash-meinel.com/branches/bzr/0.16-dev/shortcut-common-ancestor

------------------------------------------------------------
revno: 2402
revision-id: john at arbash-meinel.com-20070410175723-9a3rljph39ot4e35
parent: pqm at pqm.ubuntu.com-20070405073143-8fa894c829ab5e50
committer: John Arbash Meinel <john at arbash-meinel.com>
branch nick: shortcut-common-ancestor
timestamp: Tue 2007-04-10 12:57:23 -0500
message:
  Shortcut the common_ancestor code when one tip is in the ancestry of the other.
modified:
  bzrlib/revision.py             revision.py-20050309040759-e77802c08f3999d5
-------------- next part --------------
=== modified file 'bzrlib/revision.py'
--- a/bzrlib/revision.py	2007-01-17 15:37:08 +0000
+++ b/bzrlib/revision.py	2007-04-10 17:57:23 +0000
@@ -251,11 +251,18 @@
             pb.update('Picking ancestor', 1, 3)
             graph = revision_source.get_revision_graph_with_ghosts(
                 [revision_a, revision_b])
+            # Shortcut the case where one of the tips is already included in
+            # the other graphs ancestry.
+            ancestry_a = set(graph.get_ancestry(revision_a))
+            ancestry_b = set(graph.get_ancestry(revision_b))
+            if revision_b in ancestry_a:
+                return revision_b
+            if revision_a in ancestry_b:
+                return revision_a
             # convert to a NULL_REVISION based graph.
             ancestors = graph.get_ancestors()
             descendants = graph.get_descendants()
-            common = set(graph.get_ancestry(revision_a)).intersection(
-                     set(graph.get_ancestry(revision_b)))
+            common = ancestry_a.intersection(ancestry_b)
             descendants[NULL_REVISION] = {}
             ancestors[NULL_REVISION] = []
             for root in graph.roots: