[PATCH 4 of 4] revset: added lazyset implementation to author revset

[Lucas Moscovicz]

# HG changeset patch
# User Lucas Moscovicz <lmoscovicz at fb.com>
# Date 1391016151 28800
#      Wed Jan 29 09:22:31 2014 -0800
# Node ID 9bca7c192a62d916e3a91cc305db9d7594ffcb03
# Parent  9e46d74473bc918341572a5b94737a20b56e01b1
revset: added lazyset implementation to author revset

Performance benchmarking:

$ time hg log -qr "first(author(mpm))"
0:9117c6561b0b

real  0m3.486s
user  0m3.317s
sys 0m0.077s

$ time ./hg log -qr "first(author(mpm))"
0:9117c6561b0b

real  0m0.551s
user  0m0.295s
sys 0m0.072s

diff --git a/mercurial/revset.py b/mercurial/revset.py
--- a/mercurial/revset.py
+++ b/mercurial/revset.py
@@ -347,8 +347,7 @@
     # i18n: "author" is a keyword
     n = encoding.lower(getstring(x, _("author requires a string")))
     kind, pattern, matcher = _substringmatcher(n)
-    return baseset([r for r in subset if
-        matcher(encoding.lower(repo[r].user()))])
+    return lazyset(subset, lambda x: matcher(encoding.lower(repo[x].user())))
 
 def bisect(repo, subset, x):
     """``bisect(string)``