mercurial/rewriteutil.py

discovery: new devel.discovery.randomize option

By default, this is True, but setting it to False is a uniform
way to kill all randomness in integration tests such as test-setdiscovery.t

By "uniform" we mean that it can be passed to implementations in other
languages, for which the monkey-patching of random.sample would be
irrelevant.

In the above mentioned test file, we use it right away,
replacing the adhoc extension that had the same purpose, and to derandomize a
case with many round-trips, that we'll need to behave uniformly in the Rust
version.

Differential Revision: https://phab.mercurial-scm.org/D6427

# 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)