From patchwork Thu Jun 28 13:42:56 2018
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Subject: [3, of,
 3] revset: move lookup of first ancestor() candidate out of the loop
From: Yuya Nishihara <yuya@tcha.org>
X-Patchwork-Id: 32482
Message-Id: <0005175b53bb3f829578.1530193376@mimosa>
To: mercurial-devel@mercurial-scm.org
Date: Thu, 28 Jun 2018 22:42:56 +0900

# HG changeset patch
# User Yuya Nishihara <yuya@tcha.org>
# Date 1529159200 -32400
#      Sat Jun 16 23:26:40 2018 +0900
# Node ID 0005175b53bb3f829578757c1c34eab60c7c42a8
# Parent  fe4560fa5db2f1ee11cff233c55b7685e891517a
revset: move lookup of first ancestor() candidate out of the loop

diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -311,14 +311,15 @@ def ancestor(repo, subset, x):
     Will return empty list when passed no args.
     Greatest common ancestor of a single changeset is that changeset.
     """
-    anc = None
-    for r in orset(repo, fullreposet(repo), x, order=anyorder):
-        if anc is None:
-            anc = repo[r]
-        else:
-            anc = anc.ancestor(repo[r])
+    reviter = iter(orset(repo, fullreposet(repo), x, order=anyorder))
+    try:
+        anc = repo[next(reviter)]
+    except StopIteration:
+        return baseset()
+    for r in reviter:
+        anc = anc.ancestor(repo[r])
 
-    if anc is not None and anc.rev() in subset:
+    if anc.rev() in subset:
         return baseset([anc.rev()])
     return baseset()