view mercurial/node.py @ 35012:d80380ba8e7d

changegroup: use any node, not min(), in treemanifest's generatemanifests

This is fixing quadratic behavior, which is probably not noticeable in the
common case, but if a very large directory gets added here, it can get pretty
bad. This was noticed because we had some pushes that spent >25s in changegroup
generation calling min() here, according to profiling.

The original reasoning for min() being used in 829d369fc5a8 was that, at that
point in the series, we were adding almost everything to tmfnodes during the
first iteration through the loop , so we needed to avoid sending child
directories before parents. Later changes made it so that the child directories
were added only when we visited the parent directory (not all of them on the
first iteration), so this is no longer necessary - there won't be any child
directories in tmfnodes before the parents have been sent.

This does mean that the manifests are now exchanged unordered, whereas
previously we would essentially do [a, b, b/c, b/c/d, e], we now can send a, b,
and e in any order; b/c must still follow b, and b/c/d must still follow b/c.

Differential Revision: https://phab.mercurial-scm.org/D1351

# 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.

from __future__ import absolute_import

import binascii

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

nullrev = -1
nullid = b"\0" * 20
nullhex = hex(nullid)

# Phony node value to stand-in for new files in some uses of
# manifests.
newnodeid = '!' * 20
addednodeid = ('0' * 15) + 'added'
modifiednodeid = ('0' * 12) + 'modified'

wdirnodes = {newnodeid, addednodeid, modifiednodeid}

# pseudo identifiers for working directory
# (they are experimental, so don't add too many dependencies on them)
wdirrev = 0x7fffffff
wdirid = b"\xff" * 20
wdirhex = hex(wdirid)

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