Rev 3510: Shortcut when one side dominates, though it would be better to do so earlier. in http://bzr.arbash-meinel.com/branches/bzr/1.6-dev/merge3_per_file

[John Arbash Meinel]

At http://bzr.arbash-meinel.com/branches/bzr/1.6-dev/merge3_per_file

------------------------------------------------------------
revno: 3510
revision-id: john at arbash-meinel.com-20080621014242-hq64iwxo0ldvayqy
parent: john at arbash-meinel.com-20080621012108-gd43ci897wohmgj1
committer: John Arbash Meinel <john at arbash-meinel.com>
branch nick: merge3_per_file
timestamp: Fri 2008-06-20 20:42:42 -0500
message:
  Shortcut when one side dominates, though it would be better to do so earlier.
-------------- next part --------------
=== modified file 'bzrlib/merge.py'
--- a/bzrlib/merge.py	2008-06-21 01:21:08 +0000
+++ b/bzrlib/merge.py	2008-06-21 01:42:42 +0000
@@ -1380,16 +1380,30 @@
         self.a_rev = a_rev
         self.b_rev = b_rev
         self.vf = vf
-        self._build_weave()
+        self.graph = _mod_graph.Graph(self.vf)
+        heads = self.graph.heads((a_rev, b_rev))
+        if len(heads) == 1:
+            # one side dominates, so we can just return its values, yay for
+            # per-file graphs
+            # Ideally we would know that before we get this far
+            self._head = heads.pop()
+            if self._head == a_rev:
+                other = b_rev
+            else:
+                other = a_rev
+            note('found dominating revision for %s\n%s > %s', self.vf,
+                 self._head, other)
+        else:
+            self._head = None
+            self._build_weave()
 
     def _find_recursive_lcas(self):
         """Find all the ancestors back to a unique lca"""
         cur_ancestors = (self.a_rev, self.b_rev)
         note('finding lcas for %s:\n%s', self.vf, cur_ancestors)
-        graph = _mod_graph.Graph(self.vf)
         ancestors = [cur_ancestors]
         while True:
-            next_lcas = graph.find_lca(*cur_ancestors)
+            next_lcas = self.graph.find_lca(*cur_ancestors)
             ancestors.append(next_lcas)
             if len(next_lcas) == 0: 
                 ancestors[-1] = (NULL_REVISION,)
@@ -1443,6 +1457,14 @@
         are combined, they are written out in the format described in
         VersionedFile.plan_merge
         """
+        if self._head is not None: # There was a single head
+            if self._head == self.a_rev:
+                plan = 'new-a'
+            else:
+                assert self._head == self.b_rev
+                plan = 'new-b'
+            lines = self.vf.get_lines(self._head)
+            return ((plan, line) for line in lines)
         return self._weave.plan_merge(self.a_rev, self.b_rev)