--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hgext3rd/evolve/compat.py	Tue May 30 13:16:43 2017 +0200
@@ -0,0 +1,57 @@
+# Copyright 2017 Octobus <contact@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.
+"""
+Compatibility module
+"""
+
+from mercurial import (
+    hg,
+    obsolete
+)
+
+from . import (
+    exthelper,
+)
+
+eh = exthelper.exthelper()
+
+if not hasattr(hg, '_copycache'):
+    # exact copy of relevantmarkers as in Mercurial-176d1a0ce385
+    # this fixes relevant markers computation for version < hg-4.3
+    @eh.wrapfunction(obsolete.obsstore, 'relevantmarkers')
+    def relevantmarkers(orig, self, nodes):
+        """return a set of all obsolescence markers relevant to a set of nodes.
+
+        "relevant" to a set of nodes mean:
+
+        - marker that use this changeset as successor
+        - prune marker of direct children on this changeset
+        - recursive application of the two rules on precursors of these markers
+
+        It is a set so you cannot rely on order.
+
+        Backport of mercurial changeset 176d1a0ce385 for version < 4.3
+        """
+
+        pendingnodes = set(nodes)
+        seenmarkers = set()
+        seennodes = set(pendingnodes)
+        precursorsmarkers = self.precursors
+        succsmarkers = self.successors
+        children = self.children
+        while pendingnodes:
+            direct = set()
+            for current in pendingnodes:
+                direct.update(precursorsmarkers.get(current, ()))
+                pruned = [m for m in children.get(current, ()) if not m[1]]
+                direct.update(pruned)
+                pruned = [m for m in succsmarkers.get(current, ()) if not m[1]]
+                direct.update(pruned)
+            direct -= seenmarkers
+            pendingnodes = set([m[0] for m in direct])
+            seenmarkers |= direct
+            pendingnodes -= seennodes
+            seennodes |= pendingnodes
+        return seenmarkers