diff -r edc8504bc26b -r 4cabeea6d214 hgext/hooklib/enforce_draft_commits.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hgext/hooklib/enforce_draft_commits.py	Sat Sep 07 14:50:39 2019 +0200
@@ -0,0 +1,45 @@
+# 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.
+
+"""enforce_draft_commits us a hook to ensure that all new changesets are
+in the draft phase. This allows enforcing policies for work-in-progress
+changes in overlay repositories, i.e. a shared hidden repositories with
+different views for work-in-progress code and public history.
+
+Usage:
+  [hooks]
+  pretxnclose-phase.enforce_draft_commits = \
+    python:hgext.hooklib.enforce_draft_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"pretxnclose-phase":
+        raise error.Abort(
+            _(b'Unsupported hook type %r') % pycompat.bytestr(hooktype)
+        )
+    ctx = repo.unfiltered()[node]
+    if kwargs['oldphase']:
+        raise error.Abort(
+            _(b'Phase change from %r to %r for %s rejected')
+            % (
+                pycompat.bytestr(kwargs['oldphase']),
+                pycompat.bytestr(kwargs['phase']),
+                ctx,
+            )
+        )
+    elif kwargs['phase'] != b'draft':
+        raise error.Abort(
+            _(b'New changeset %s in phase %r rejected')
+            % (ctx, pycompat.bytestr(kwargs['phase']))
+        )