templates: fix `revset('parents()') % ...` in amend message template I don't understand why, but putting `revset('parents()') % {desc}` in the commit message template for amend resulted in a crash because `memctx.hex()` did `hex(self.node())` and its node was None. This patch fixes that. Martin von Zweigbergk <martinvonz@google.com> Differential Revision: https://phab.mercurial-scm.org/D10707

--- a/mercurial/context.py	Thu Apr 15 19:54:03 2021 +0200
+++ b/mercurial/context.py	Tue May 11 12:22:26 2021 -0700
@@ -1392,6 +1392,9 @@
     def __bytes__(self):
         return bytes(self._parents[0]) + b"+"
 
+    def hex(self):
+        self._repo.nodeconstants.wdirhex
+
     __str__ = encoding.strmethod(__bytes__)
 
     def __nonzero__(self):