view mercurial/rewriteutil.py @ 35714:113281667205

githelp: vendor Facebook authored extension

This commit vendors the Facebook-authored "githelp" extension. This
extension provides a "githelp" command that can be used to try to
convert a `git` command to its Mercurial equivalent. This functionality
is useful for Git users learning Mercurial.

The extension was copied from the
repository at revision 32ceeccb832c433b36e9af8196814b8e5a526775. The
following modifications were made:

* The "testedwith" value has been changed to match core's conventions.
* Support for a custom footer has been removed, as it is Facebook
  specific. The feature is useful. But the implementation wasn't
  appropriate for core.
* A test referencing "tweakdefaults" has been removed.
* Imports changed to match Mercurial's style convention.
* Double newlines in test removed.
* Pager activation changed to ui.pager().
* Initial line of githelp.py changed to add description of file.

The removal of the custom footer code was the only significant
source change. The rest were mostly cosmetic.

There are still some Facebook-isms in the extension. I'll address
these as follow-ups.

.. feature:: githelp extension

   The "githelp" extension provides the ``hg githelp`` command. This
   command attempts to convert a ``git`` command to its Mercurial
   equivalent. The extension can be useful to Git users new to
   Mercurial.

Differential Revision: https://phab.mercurial-scm.org/D1722

# 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)

    publicrevs = repo.revs('%ld and public()', revs)
    if len(repo[None].parents()) > 1:
        raise error.Abort(_("cannot %s while merging") % action)

    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)