mercurial/rewriteutil.py

context: introduce p[12]copies() methods and debugp[12]copies commands

As mentioned earlier, I'm working on support for storing copy metadata
in the changeset instead of in the filelog.

In order to transition a repo from storing metadata in filelogs to
storing it in the changeset, I'm going to provide a config option for
reading the metadata from the changeset, but falling back to getting
it from the filelog if it's not in the changeset. In this compatiblity
mode, the changeset-optmized algorithms will be used. We will then
need to convert the filelog copy metadata to look like that provided
by changeset copy metadata. This patch introduces methods that do just
that.

By having these methods here, we can start writing changeset-optimized
algorithms that should work already before we add any support for
storing the metadata in the changesets.

This commit also includes new debugp[12]copies commands and exercises
them in test-copies.t.

Differential Revision: https://phab.mercurial-scm.org/D5990

# rewriteutil.py - utility functions for rewriting changesets
#
# Copyright 2017 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 (
    error,
    node,
    obsolete,
    revset,
)

def precheck(repo, revs, action='rewrite'):
    """check if revs can be rewritten
    action is used to control the error message.

    Make sure this function is called after taking the lock.
    """
    if node.nullrev in revs:
        msg = _("cannot %s null changeset") % (action)
        hint = _("no changeset checked out")
        raise error.Abort(msg, hint=hint)

    if len(repo[None].parents()) > 1:
        raise error.Abort(_("cannot %s while merging") % action)

    publicrevs = repo.revs('%ld and public()', revs)
    if publicrevs:
        msg = _("cannot %s public changesets") % (action)
        hint = _("see 'hg help phases' for details")
        raise error.Abort(msg, hint=hint)

    newunstable = disallowednewunstable(repo, revs)
    if newunstable:
        raise error.Abort(_("cannot %s changeset with children") % action)

def disallowednewunstable(repo, revs):
    """Checks whether editing the revs will create new unstable changesets and
    are we allowed to create them.

    To allow new unstable changesets, set the config:
        `experimental.evolution.allowunstable=True`
    """
    allowunstable = obsolete.isenabled(repo, obsolete.allowunstableopt)
    if allowunstable:
        return revset.baseset()
    return repo.revs("(%ld::) - %ld", revs, revs)