# HG changeset patch
# User Martin von Zweigbergk <martinvonz@google.com>
# Date 2019-01-24 20:47:54
# Node ID a728ef2f9b15e8b4a7d5d15928c26c074293da92
# Parent  5079242abef9601a1007015a9b5191d40553009d

revpair: clarify check for empty revset

Differential Revision: https://phab.mercurial-scm.org/D5688

diff --git a/mercurial/scmutil.py b/mercurial/scmutil.py
--- a/mercurial/scmutil.py
+++ b/mercurial/scmutil.py
@@ -672,11 +672,12 @@ def revpair(repo, revs):
 
     l = revrange(repo, revs)
 
+    if not l:
+        raise error.Abort(_('empty revision range'))
+
     first = l.first()
     second = l.last()
 
-    if first is None:
-        raise error.Abort(_('empty revision range'))
     if (first == second and len(revs) >= 2
         and not all(revrange(repo, [r]) for r in revs)):
         raise error.Abort(_('empty revision on one side of range'))