mercurial/scmutil.py

--- a/mercurial/scmutil.py	Mon Oct 22 15:51:01 2018 +0200
+++ b/mercurial/scmutil.py	Mon Oct 22 11:34:35 2018 -0700
@@ -495,6 +495,8 @@
     # which would be unacceptably slow. so we look for hash collision in
     # unfiltered space, which means some hashes may be slightly longer.
 
+    minlength=max(minlength, 1)
+
     def disambiguate(prefix):
         """Disambiguate against revnums."""
         if repo.ui.configbool('experimental', 'revisions.prefixhexnode'):