mercurial/node.py

revset: make use of natively-computed set for 'draft()' and 'secret()'

If the computation of a set for each phase (done in C) is available,
we use it directly instead of applying a simple filter. This give a
massive speed-up in the vast majority of cases.

On my mercurial repo with about 15000 out of 40000 draft changesets:

revset: draft()
   plain         min           first         last
0) 0.011201      0.019950      0.009844      0.000074
1) 0.000284   2% 0.000312   1% 0.000314   3% 0.000315 x4.3

Bad performance for "last" come from the handling of the 15000 elements set
(memory allocation, filtering hidden changesets (99% of it) etc. compared to
applying the filter only on a handfuld of revisions (the first draft changesets
being close of tip).

This is not seen as an issue since:

* Timing is still pretty good and in line with all the other one,
* Current user of Vanilla Mercurial will not have 1/3 of their repo draft,

This bad effect disappears when phase's set is smaller. (about 200 secrets):

revset: secret()
   plain         min           first         last
0) 0.011181      0.022228      0.010851      0.000452
1) 0.000058   0% 0.000084   0% 0.000087   0% 0.000087  19%

# node.py - basic nodeid manipulation for mercurial
#
# Copyright 2005, 2006 Matt Mackall <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

import binascii

nullrev = -1
nullid = "\0" * 20

# This ugly style has a noticeable effect in manifest parsing
hex = binascii.hexlify
bin = binascii.unhexlify

def short(node):
    return hex(node[:6])