diff mercurial/simplemerge.py @ 46843:728d89f6f9b1

refactor: prefer checks against nullrev over nullid

A common pattern is using a changeset context and obtaining the node to
compare against nullid. Change this to obtain the nullrev instead. In
the future, the nullid becomes a property of the repository and is no
longer a global constant, so using nullrev is much easier to reason
about. Python function call overhead makes the difference moot, but
future changes will result in more dictionary lookups otherwise, so
prefer the simpler pattern.

Differential Revision: https://phab.mercurial-scm.org/D10290

--- a/mercurial/simplemerge.py	Tue Mar 30 02:33:12 2021 +0200
+++ b/mercurial/simplemerge.py	Tue Mar 30 02:32:30 2021 +0200
@@ -19,7 +19,7 @@
 from __future__ import absolute_import
 
 from .i18n import _
-from .node import nullid
+from .node import nullrev
 from . import (
     error,
     mdiff,
@@ -427,7 +427,7 @@
 def is_not_null(ctx):
     if not util.safehasattr(ctx, "node"):
         return False
-    return ctx.node() != nullid
+    return ctx.rev() != nullrev
 
 
 def _mergediff(m3, name_a, name_b, name_base):