[PATCH 3 of 6] revlog: slightly tune group() by not going rev->node->rev

[Peter Arrenbrecht]

# HG changeset patch
# User Peter Arrenbrecht <peter.arrenbrecht at gmail.com>
# Date 1242309621 -7200
# Node ID 8e4626b3920fb1c3a142c754b557b1cdba25e477
# Parent  c236b8986ed27ad39e646e3683000e1e40493a9d
revlog: slightly tune group() by not going rev->node->rev

diff --git a/mercurial/revlog.py b/mercurial/revlog.py
--- a/mercurial/revlog.py
+++ b/mercurial/revlog.py
@@ -1149,16 +1149,17 @@
         have this parent as it has all history before these
         changesets. parent is parent[0]
         """
-        revs = [self.rev(n) for n in nodelist]
 
         # if we don't have any revisions touched by these changesets, bail
-        if not revs:
+        if not nodelist:
             yield changegroup.closechunk()
             return
 
+        revs = [self.rev(n) for n in nodelist]
+
         # add the parent of the first rev
-        p = self.parents(self.node(revs[0]))[0]
-        revs.insert(0, self.rev(p))
+        p = self.parentrevs(revs[0])[0]
+        revs.insert(0, p)
 
         # build deltas
         for d in xrange(0, len(revs) - 1):