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
# amend.py - provide the amend command
#
# 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.
"""provide the amend command (EXPERIMENTAL)
This extension provides an ``amend`` command that is similar to
``commit --amend`` but does not prompt an editor.
"""
from mercurial.i18n import _
from mercurial import (
cmdutil,
commands,
registrar,
)
# Note for extension authors: ONLY specify testedwith = 'ships-with-hg-core' for
# extensions which SHIP WITH MERCURIAL. Non-mainline extensions should
# be specifying the version(s) of Mercurial they are tested with, or
# leave the attribute unspecified.
testedwith = b'ships-with-hg-core'
cmdtable = {}
command = registrar.command(cmdtable)
@command(
b'amend',
[
(
b'A',
b'addremove',
None,
_(b'mark new/missing files as added/removed before committing'),
),
(b'e', b'edit', None, _(b'invoke editor on commit messages')),
(b'i', b'interactive', None, _(b'use interactive mode')),
(
b'',
b'close-branch',
None,
_(b'mark a branch as closed, hiding it from the branch list'),
),
(b's', b'secret', None, _(b'use the secret phase for committing')),
(b'n', b'note', b'', _(b'store a note on the amend')),
]
+ cmdutil.walkopts
+ cmdutil.commitopts
+ cmdutil.commitopts2
+ cmdutil.commitopts3,
_(b'[OPTION]... [FILE]...'),
helpcategory=command.CATEGORY_COMMITTING,
inferrepo=True,
)
def amend(ui, repo, *pats, **opts):
"""amend the working copy parent with all or specified outstanding changes
Similar to :hg:`commit --amend`, but reuse the commit message without
invoking editor, unless ``--edit`` was set.
See :hg:`help commit` for more details.
"""
cmdutil.check_note_size(opts)
with repo.wlock(), repo.lock():
if not opts.get('logfile'):
opts['message'] = opts.get('message') or repo[b'.'].description()
opts['amend'] = True
return commands._docommit(ui, repo, *pats, **opts)