annotate hgext/split.py @ 38717:aa21a9ad46ea

sparse-revlog: new requirement enabled with format.sparse-revlog

The meaning of the new 'sparse-revlog' requirement is that the revlogs are
allowed to contain wider delta chains with larger holes between the interesting
chunks. These sparse delta chains should be read in several chunks to avoid a
potential explosion of memory usage.

Former version won't know how to read a delta chain in several chunks. They
would keep reading them in a single read, and therefore would be subject to the
potential memory explosion. Hence this new requirement: only versions having
support of sparse-revlog reading should be allowed to read such a revlog.

Implementation of this new algorithm and tools to enable or disable the
requirement will follow in the next changesets.

# split.py - split a changeset into smaller ones
#
# Copyright 2015 Laurent Charignon <[e-mail]>
# 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.
"""command to split a changeset into smaller ones (EXPERIMENTAL)"""

from __future__ import absolute_import

from mercurial.i18n import _

from mercurial.node import (
    nullid,
    short,
)

from mercurial import (
    bookmarks,
    cmdutil,
    commands,
    error,
    hg,
    obsolete,
    phases,
    pycompat,
    registrar,
    revsetlang,
    scmutil,
)

# allow people to use split without explicitly enabling rebase extension
from . import (
    rebase,
)

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

# 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'

@command('^split',
    [('r', 'rev', '', _("revision to split"), _('REV')),
     ('', 'rebase', True, _('rebase descendants after split')),
    ] + cmdutil.commitopts2,
    _('hg split [--no-rebase] [[-r] REV]'))
def split(ui, repo, *revs, **opts):
    """split a changeset into smaller ones

    Repeatedly prompt changes and commit message for new changesets until there
    is nothing left in the original changeset.

    If --rev was not given, split the working directory parent.

    By default, rebase connected non-obsoleted descendants onto the new
    changeset. Use --no-rebase to avoid the rebase.
    """
    opts = pycompat.byteskwargs(opts)
    revlist = []
    if opts.get('rev'):
        revlist.append(opts.get('rev'))
    revlist.extend(revs)
    with repo.wlock(), repo.lock(), repo.transaction('split') as tr:
        revs = scmutil.revrange(repo, revlist or ['.'])
        if len(revs) > 1:
            raise error.Abort(_('cannot split multiple revisions'))

        rev = revs.first()
        ctx = repo[rev]
        if rev is None or ctx.node() == nullid:
            ui.status(_('nothing to split\n'))
            return 1
        if ctx.node() is None:
            raise error.Abort(_('cannot split working directory'))

        # rewriteutil.precheck is not very useful here because:
        # 1. null check is done above and it's more friendly to return 1
        #    instead of abort
        # 2. mergestate check is done below by cmdutil.bailifchanged
        # 3. unstable check is more complex here because of --rebase
        #
        # So only "public" check is useful and it's checked directly here.
        if ctx.phase() == phases.public:
            raise error.Abort(_('cannot split public changeset'),
                              hint=_("see 'hg help phases' for details"))

        descendants = list(repo.revs('(%d::) - (%d)', rev, rev))
        alloworphaned = obsolete.isenabled(repo, obsolete.allowunstableopt)
        if opts.get('rebase'):
            # Skip obsoleted descendants and their descendants so the rebase
            # won't cause conflicts for sure.
            torebase = list(repo.revs('%ld - (%ld & obsolete())::',
                                      descendants, descendants))
            if not alloworphaned and len(torebase) != len(descendants):
                raise error.Abort(_('split would leave orphaned changesets '
                                    'behind'))
        else:
            if not alloworphaned and descendants:
                raise error.Abort(
                    _('cannot split changeset with children without rebase'))
            torebase = ()

        if len(ctx.parents()) > 1:
            raise error.Abort(_('cannot split a merge changeset'))

        cmdutil.bailifchanged(repo)

        # Deactivate bookmark temporarily so it won't get moved unintentionally
        bname = repo._activebookmark
        if bname and repo._bookmarks[bname] != ctx.node():
            bookmarks.deactivate(repo)

        wnode = repo['.'].node()
        top = None
        try:
            top = dosplit(ui, repo, tr, ctx, opts)
        finally:
            # top is None: split failed, need update --clean recovery.
            # wnode == ctx.node(): wnode split, no need to update.
            if top is None or wnode != ctx.node():
                hg.clean(repo, wnode, show_stats=False)
            if bname:
                bookmarks.activate(repo, bname)
        if torebase and top:
            dorebase(ui, repo, torebase, top)

def dosplit(ui, repo, tr, ctx, opts):
    committed = [] # [ctx]

    # Set working parent to ctx.p1(), and keep working copy as ctx's content
    # NOTE: if we can have "update without touching working copy" API, the
    # revert step could be cheaper.
    hg.clean(repo, ctx.p1().node(), show_stats=False)
    parents = repo.changelog.parents(ctx.node())
    ui.pushbuffer()
    cmdutil.revert(ui, repo, ctx, parents)
    ui.popbuffer() # discard "reverting ..." messages

    # Any modified, added, removed, deleted result means split is incomplete
    incomplete = lambda repo: any(repo.status()[:4])

    # Main split loop
    while incomplete(repo):
        if committed:
            header = (_('HG: Splitting %s. So far it has been split into:\n')
                      % short(ctx.node()))
            for c in committed:
                firstline = c.description().split('\n', 1)[0]
                header += _('HG: - %s: %s\n') % (short(c.node()), firstline)
            header += _('HG: Write commit message for the next split '
                        'changeset.\n')
        else:
            header = _('HG: Splitting %s. Write commit message for the '
                       'first split changeset.\n') % short(ctx.node())
        opts.update({
            'edit': True,
            'interactive': True,
            'message': header + ctx.description(),
        })
        commands.commit(ui, repo, **pycompat.strkwargs(opts))
        newctx = repo['.']
        committed.append(newctx)

    if not committed:
        raise error.Abort(_('cannot split an empty revision'))

    scmutil.cleanupnodes(repo, {ctx.node(): [c.node() for c in committed]},
                         operation='split', fixphase=True)

    return committed[-1]

def dorebase(ui, repo, src, destctx):
    rebase.rebase(ui, repo, rev=[revsetlang.formatspec('%ld', src)],
                  dest=revsetlang.formatspec('%d', destctx.rev()))