diff hgext/hooklib/reject_merge_commits.py @ 44413:4cabeea6d214

hgext: start building a library for simple hooks

Many workflows depend on hooks to enforce certain policies, e.g. to
prevent forced pushes. The Mercurial Guide includes some cases and
Google can help finding others, but it can save users a lot of time
if hg itself has a couple of examples for further customization.

Differential Revision: https://phab.mercurial-scm.org/D6825

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hgext/hooklib/reject_merge_commits.py	Sat Sep 07 14:50:39 2019 +0200
@@ -0,0 +1,45 @@
+# Copyright 2020 Joerg Sonnenberger <[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.
+
+"""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
+            )