diff -r e58e234096de -r 77b8588dd84e mercurial/requirements.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mercurial/requirements.py	Sat Aug 08 16:24:12 2020 +0530
@@ -0,0 +1,22 @@
+# requirements.py - objects and functions related to repository requirements
+#
+# Copyright 2005-2007 Matt Mackall <mpm@selenic.com>
+#
+# 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
+
+# When narrowing is finalized and no longer subject to format changes,
+# we should move this to just "narrow" or similar.
+NARROW_REQUIREMENT = b'narrowhg-experimental'
+
+# Enables sparse working directory usage
+SPARSE_REQUIREMENT = b'exp-sparse'
+
+# Enables the internal phase which is used to hide changesets instead
+# of stripping them
+INTERNAL_PHASE_REQUIREMENT = b'internal-phase'
+
+# Stores manifest in Tree structure
+TREEMANIFEST_REQUIREMENT = b'treemanifest'