# split.py - split a changeset into smaller ones

#

# Copyright 2015 Laurent Charignon <lcharignon@fb.com>

# 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,

    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.

    """

    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, **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')

    return committed[-1]

def dorebase(ui, repo, src, dest):

    rebase.rebase(ui, repo, rev=[revsetlang.formatspec('%ld', src)],

                  dest=revsetlang.formatspec('%d', dest))