bisect: avoid copying ancestor list for non-merge commits
During a bisection, hg needs to compute a list of all ancestors for every
candidate commit. This is accomplished via a bottom-up traversal of the set of
candidates, during which each revision's ancestor list is populated using the
ancestor list of its parent(s). Previously, this involved copying the entire
list, which could be very long in if the bisection range was large.
To help improve this, we can observe that each candidate commit is visited
exactly once, at which point its ancestor list is copied into its children's
lists and then dropped. In the case of non-merge commits, a commit's ancestor
list consists exactly of its parent's list plus itself. This means that we can
trivially reuse the parent's existing list for one of its non-merge children,
which avoids copying entirely if that commit is the parent's only child. This
makes bisections over linear ranges of commits much faster.
During some informal testing in the large publicly-available `mozilla-central`
repository, this noticeably sped up bisections over large ranges of history:
Setup:
$ cd mozilla-central
$ hg bisect --reset
$ hg bisect --good 0
$ hg log -r tip -T '{rev}\n'
628417
Test:
$ time hg bisect --bad tip --noupdate
Before:
real 3m35.927s
user 3m35.553s
sys 0m0.319s
After:
real 1m41.142s
user 1m40.810s
sys 0m0.285s
# pointer.py - Git-LFS pointer serialization
#
# Copyright 2017 Facebook, Inc.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
import re
from mercurial.i18n import _
from mercurial import (
error,
pycompat,
)
from mercurial.utils import stringutil
class InvalidPointer(error.StorageError):
pass
class gitlfspointer(dict):
VERSION = b'https://git-lfs.github.com/spec/v1'
def __init__(self, *args, **kwargs):
self[b'version'] = self.VERSION
super(gitlfspointer, self).__init__(*args)
self.update(pycompat.byteskwargs(kwargs))
@classmethod
def deserialize(cls, text):
try:
return cls(l.split(b' ', 1) for l in text.splitlines()).validate()
except ValueError: # l.split returns 1 item instead of 2
raise InvalidPointer(
_(b'cannot parse git-lfs text: %s') % stringutil.pprint(text)
)
def serialize(self):
sortkeyfunc = lambda x: (x[0] != b'version', x)
items = sorted(self.validate().items(), key=sortkeyfunc)
return b''.join(b'%s %s\n' % (k, v) for k, v in items)
def oid(self):
return self[b'oid'].split(b':')[-1]
def size(self):
return int(self[b'size'])
# regular expressions used by _validate
# see https://github.com/git-lfs/git-lfs/blob/master/docs/spec.md
_keyre = re.compile(br'\A[a-z0-9.-]+\Z')
_valuere = re.compile(br'\A[^\n]*\Z')
_requiredre = {
b'size': re.compile(br'\A[0-9]+\Z'),
b'oid': re.compile(br'\Asha256:[0-9a-f]{64}\Z'),
b'version': re.compile(br'\A%s\Z' % stringutil.reescape(VERSION)),
}
def validate(self):
"""raise InvalidPointer on error. return self if there is no error"""
requiredcount = 0
for k, v in self.items():
if k in self._requiredre:
if not self._requiredre[k].match(v):
raise InvalidPointer(
_(b'unexpected lfs pointer value: %s=%s')
% (k, stringutil.pprint(v))
)
requiredcount += 1
elif not self._keyre.match(k):
raise InvalidPointer(_(b'unexpected lfs pointer key: %s') % k)
if not self._valuere.match(v):
raise InvalidPointer(
_(b'unexpected lfs pointer value: %s=%s')
% (k, stringutil.pprint(v))
)
if len(self._requiredre) != requiredcount:
miss = sorted(set(self._requiredre.keys()).difference(self.keys()))
raise InvalidPointer(
_(b'missing lfs pointer keys: %s') % b', '.join(miss)
)
return self
deserialize = gitlfspointer.deserialize