D1502: rewriteutil: add utility function to check if we can create new unstable cset

[pulkit (Pulkit Goyal)]

pulkit created this revision.
Herald added a subscriber: mercurial-devel.
Herald added a reviewer: hg-reviewers.

REVISION SUMMARY
  This patch adds a new file which will contain utility functions related to
  rewritting changesets. It also adds a utility function to check if the
  rewritting operation creates new unstable changesets and are we allowed to
  create them.
  
  This rewriteutil.py introduced in this patch and the utility functions added in
  the upcoming patches exists in the evolve extension are being ported from there.

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D1502

AFFECTED FILES
  mercurial/rewriteutil.py

CHANGE DETAILS

diff --git a/mercurial/rewriteutil.py b/mercurial/rewriteutil.py
new file mode 100644
--- /dev/null
+++ b/mercurial/rewriteutil.py
@@ -0,0 +1,25 @@
+# rewriteutil.py - utility functions for rewriting changesets
+#
+# Copyright 2017 Octobus <contact at octobus.net>
+#
+# This software may be used and distributed according to the terms of the
+# GNU General Public License version 2 or any later version.
+
+from mercurial import (
+    obsolete,
+    revset,
+)
+
+from mercurial.i18n import _
+
+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.allounstable=True`
+    """
+    allowunstable = obsolete.isenabled(repo, obsolete.allowunstableopt)
+    if allowunstable:
+        return revset.baseset()
+    return repo.revs("(%ld::) - %ld", revs, revs)



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