# Copyright 2020 Joerg Sonnenberger <joerg@bec.de>

#

# This software may be used and distributed according to the terms of the

# GNU General Public License version 2 or any later version.

"""reject_merge_commits is a hook to check new changesets for merge commits.

Merge commits are allowed only between different branches, i.e. merging

a feature branch into the main development branch. This can be used to

enforce policies for linear commit histories.

Usage:

  [hooks]

  pretxnchangegroup.reject_merge_commits = \

    python:hgext.hooklib.reject_merge_commits.hook

"""

from __future__ import absolute_import

from mercurial.i18n import _

from mercurial import (

    error,

    pycompat,

)

def hook(ui, repo, hooktype, node=None, **kwargs):

    if hooktype != b"pretxnchangegroup":

        raise error.Abort(

            _(b'Unsupported hook type %r') % pycompat.bytestr(hooktype)

        )

    ctx = repo.unfiltered()[node]

    for rev in repo.changelog.revs(start=ctx.rev()):

        rev = repo[rev]

        parents = rev.parents()

        if len(parents) < 2:

            continue

        if all(repo[p].branch() == rev.branch() for p in parents):

            raise error.Abort(

                _(

                    b'%s rejected as merge on the same branch. '

                    b'Please consider rebase.'

                )

                % rev

            )