view hgext/amend.py @ 42743:8c9a6adec67a

rust-discovery: using the children cache in add_missing

The DAG range computation often needs to get back to very old
revisions, and turns out to be disproportionately long, given
that the end goal is to remove the descendents of the given
missing revisons from the undecided set.

The fast iteration capabilities available in the Rust case make
it possible to avoid the DAG range entirely, at the cost of
precomputing the children cache, and to simply iterate on
children of the given missing revisions.

This is a case where staying on the same side of the interface
between the two languages has clear benefits.

On discoveries with initial undecided sets
small enough to bypass sampling entirely, the total cost of
computing the children cache and the subsequent iteration
becomes better than the Python + C counterpart, which relies on
reachableroots2.

For example, on a repo with more than one million revisions with
an initial undecided set of 11 elements, we get these figures:

Rust version with simple iteration
  addcommons: 57.287us
  first undecided computation: 184.278334ms
  first children cache computation: 131.056us
  addmissings iteration: 42.766us
  first addinfo total: 185.24 ms

Python + C version
  first addcommons: 0.29 ms
  addcommons 0.21 ms
  first undecided computation 191.35 ms
  addmissings 45.75 ms
  first addinfo total: 237.77 ms

On discoveries with large undecided sets, the initial price paid
makes the first addinfo slower than the Python + C version,
but that's more than compensated by the gain in sampling and
subsequent iterations.
Here's an extreme example with an undecided set of a million revisions:

Rust version:
  first undecided computation: 293.842629ms
  first children cache computation: 407.911297ms
  addmissings iteration: 34.312869ms
  first addinfo total: 776.02 ms
  taking initial sample
  query 2: sampling time: 1318.38 ms
  query 2; still undecided: 1005013, sample size is: 200
  addmissings: 143.062us

Python + C version:
  first undecided computation 298.13 ms
  addmissings 80.13 ms
  first addinfo total: 399.62 ms
  taking initial sample
  query 2: sampling time: 3957.23 ms
  query 2; still undecided: 1005013, sample size is: 200
  addmissings 52.88 ms

Differential Revision: https://phab.mercurial-scm.org/D6428

# 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 __future__ import absolute_import

from mercurial.i18n import _
from mercurial import (
    cmdutil,
    commands,
    error,
    pycompat,
    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 = 'ships-with-hg-core'

cmdtable = {}
command = registrar.command(cmdtable)

@command('amend',
    [('A', 'addremove', None,
      _('mark new/missing files as added/removed before committing')),
     ('e', 'edit', None, _('invoke editor on commit messages')),
     ('i', 'interactive', None, _('use interactive mode')),
     ('n', 'note', '', _('store a note on the amend')),
     ('D', 'currentdate', None,
      _('record the current date as commit date')),
    ] + cmdutil.walkopts + cmdutil.commitopts + cmdutil.commitopts2,
    _('[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.
    """
    opts = pycompat.byteskwargs(opts)
    if len(opts['note']) > 255:
        raise error.Abort(_("cannot store a note of more than 255 bytes"))
    with repo.wlock(), repo.lock():
        if not opts.get('logfile'):
            opts['message'] = opts.get('message') or repo['.'].description()
        opts['amend'] = True
        return commands._docommit(ui, repo, *pats, **pycompat.strkwargs(opts))