mercurial/diffutil.py

nodemap: also use persistent nodemap for manifest

The manifest as a different usage pattern than the changelog. First, while the
lookup in changelog are not garanteed to match, the lookup in the manifest
nodemap come from changelog and will exist in the manifest. In addition, looking
up a manifest almost always result in unpacking a manifest an operation that
rarely come cheap.

Nevertheless, using a persistent nodemap provide a significant gain for some
operations.


For our measurementw, we use `hg cat --rev REV FILE` on the our reference
mozilla-try. On this repository the persistent nodemap cache is about 29 MB in
side for a total store side of 11,988 MB

File with large history (file: b2g/config/gaia.json, revision: 195a1146daa0)

    no optimisation:                             0.358s
    using mmap for index:                        0.297s (-0.061s)
    persistent nodemap for changelog only:       0.275s (-0.024s)
    persistent nodemap for manifest too:         0.258s (-0.017s)

File with small history (file: .hgignore, revision: 195a1146daa0)

    no optimisation:                             0.377s
    using mmap for index:                        0.296s (-0.061s)
    persistent nodemap for changelog only:       0.274s (-0.022s)
    persistent nodemap for manifest too:         0.257s (-0.017s)

Same file but using a revision (8ba995b74e18) with a smaller manifest (3944829
bytes vs  10 bytes)

    no optimisation:                             0.192s (-0.185s)
    using mmap for index:                        0.131s (-0.061s)
    persistent nodemap for changelog only:       0.106s (-0.025s)
    persistent nodemap for manifest too:         0.087s (-0.019s)

Differential Revision: https://phab.mercurial-scm.org/D8410

# diffutil.py - utility functions related to diff and patch
#
# Copyright 2006 Brendan Cully <[e-mail]>
# Copyright 2007 Chris Mason <[e-mail]>
# Copyright 2018 Octobus <[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

from .i18n import _

from . import (
    mdiff,
    pycompat,
)


def diffallopts(
    ui, opts=None, untrusted=False, section=b'diff', configprefix=b''
):
    '''return diffopts with all features supported and parsed'''
    return difffeatureopts(
        ui,
        opts=opts,
        untrusted=untrusted,
        section=section,
        git=True,
        whitespace=True,
        formatchanging=True,
        configprefix=configprefix,
    )


def difffeatureopts(
    ui,
    opts=None,
    untrusted=False,
    section=b'diff',
    git=False,
    whitespace=False,
    formatchanging=False,
    configprefix=b'',
):
    '''return diffopts with only opted-in features parsed

    Features:
    - git: git-style diffs
    - whitespace: whitespace options like ignoreblanklines and ignorews
    - formatchanging: options that will likely break or cause correctness issues
      with most diff parsers
    '''

    def get(key, name=None, getter=ui.configbool, forceplain=None):
        if opts:
            v = opts.get(key)
            # diffopts flags are either None-default (which is passed
            # through unchanged, so we can identify unset values), or
            # some other falsey default (eg --unified, which defaults
            # to an empty string). We only want to override the config
            # entries from hgrc with command line values if they
            # appear to have been set, which is any truthy value,
            # True, or False.
            if v or isinstance(v, bool):
                return v
        if forceplain is not None and ui.plain():
            return forceplain
        return getter(
            section, configprefix + (name or key), untrusted=untrusted
        )

    # core options, expected to be understood by every diff parser
    buildopts = {
        b'nodates': get(b'nodates'),
        b'showfunc': get(b'show_function', b'showfunc'),
        b'context': get(b'unified', getter=ui.config),
    }
    buildopts[b'xdiff'] = ui.configbool(b'experimental', b'xdiff')

    if git:
        buildopts[b'git'] = get(b'git')

        # since this is in the experimental section, we need to call
        # ui.configbool directory
        buildopts[b'showsimilarity'] = ui.configbool(
            b'experimental', b'extendedheader.similarity'
        )

        # need to inspect the ui object instead of using get() since we want to
        # test for an int
        hconf = ui.config(b'experimental', b'extendedheader.index')
        if hconf is not None:
            hlen = None
            try:
                # the hash config could be an integer (for length of hash) or a
                # word (e.g. short, full, none)
                hlen = int(hconf)
                if hlen < 0 or hlen > 40:
                    msg = _(b"invalid length for extendedheader.index: '%d'\n")
                    ui.warn(msg % hlen)
            except ValueError:
                # default value
                if hconf == b'short' or hconf == b'':
                    hlen = 12
                elif hconf == b'full':
                    hlen = 40
                elif hconf != b'none':
                    msg = _(b"invalid value for extendedheader.index: '%s'\n")
                    ui.warn(msg % hconf)
            finally:
                buildopts[b'index'] = hlen

    if whitespace:
        buildopts[b'ignorews'] = get(b'ignore_all_space', b'ignorews')
        buildopts[b'ignorewsamount'] = get(
            b'ignore_space_change', b'ignorewsamount'
        )
        buildopts[b'ignoreblanklines'] = get(
            b'ignore_blank_lines', b'ignoreblanklines'
        )
        buildopts[b'ignorewseol'] = get(b'ignore_space_at_eol', b'ignorewseol')
    if formatchanging:
        buildopts[b'text'] = opts and opts.get(b'text')
        binary = None if opts is None else opts.get(b'binary')
        buildopts[b'nobinary'] = (
            not binary
            if binary is not None
            else get(b'nobinary', forceplain=False)
        )
        buildopts[b'noprefix'] = get(b'noprefix', forceplain=False)
        buildopts[b'worddiff'] = get(
            b'word_diff', b'word-diff', forceplain=False
        )

    return mdiff.diffopts(**pycompat.strkwargs(buildopts))