[PATCH 3 of 6 V2] revset: remove grandparent by using revsbetween

[Laurent Charignon]

# HG changeset patch
# User Laurent Charignon <lcharignon at fb.com>
# Date 1434770932 25200
#      Fri Jun 19 20:28:52 2015 -0700
# Branch stable
# Node ID 4d1b9f4def5070ac3a09dbeb396b745237a49417
# Parent  812d9212f1474df436453d08b7c71a44549524a3
revset: remove grandparent by using revsbetween

This patch is part of a series of patches to speed up the computation of
revset.revsbetween by introducing a C implementation. The main motivation is to
speed up smartlog on big repositories. At the end of the series, on our big
repositories the computation of revsbetween is 10-50x faster and smartlog on is
2x-5x faster.

Before this patch, we had a custom computation for grandparent that was very
close to the idea of revsbetween. This patch expresses grandparent with
revsbetween to reduce the amount of code.

diff --git a/mercurial/graphmod.py b/mercurial/graphmod.py
--- a/mercurial/graphmod.py
+++ b/mercurial/graphmod.py
@@ -19,6 +19,7 @@
 
 from mercurial.node import nullrev
 import util
+import revset
 
 import heapq
 
@@ -233,8 +234,6 @@
     if not revs:
         return
 
-    cl = repo.changelog
-    lowestrev = revs.min()
     gpcache = {}
 
     if repo.ui.configbool('experimental', 'graph-group-branches', False):
@@ -256,7 +255,8 @@
         for mpar in mpars:
             gp = gpcache.get(mpar)
             if gp is None:
-                gp = gpcache[mpar] = grandparent(cl, lowestrev, revs, mpar)
+                gp = gpcache[mpar] = revset.revsbetween(repo, revs, [mpar],
+                                                         includepath=False)
             if not gp:
                 parents.append(mpar)
             else:
@@ -354,24 +354,6 @@
         yield (cur, type, data, (col, color), edges)
         seen = next
 
-def grandparent(cl, lowestrev, roots, head):
-    """Return all ancestors of head in roots which revision is
-    greater or equal to lowestrev.
-    """
-    pending = set([head])
-    seen = set()
-    kept = set()
-    llowestrev = max(nullrev, lowestrev)
-    while pending:
-        r = pending.pop()
-        if r >= llowestrev and r not in seen:
-            if r in roots:
-                kept.add(r)
-            else:
-                pending.update([p for p in cl.parentrevs(r)])
-            seen.add(r)
-    return sorted(kept)
-
 def asciiedges(type, char, lines, seen, rev, parents):
     """adds edge info to changelog DAG walk suitable for ascii()"""
     if rev not in seen: