revisions: when using prefixhexnode, ensure we prefix "0" Previously, if using `experimental.revisions.disambiguatewithin` (and it didn't include rev0), and '0' was the shortest identifier in that disambiguation set, we printed it as the shortest *without* a prefix. This was because we had logic to determine "if the prefix is a pure integer, but starts with 0, we don't need to prefix with 'x': 01 is not a synonym for revision #1", but didn't handle the case where prefix == 0 (which is a pure integer, and starts with 0... but it *is* "rev0"). Differential Revision: https://phab.mercurial-scm.org/D5113

--- a/tests/test-revisions.t	Wed Oct 03 16:45:24 2018 +0300
+++ b/tests/test-revisions.t	Tue Oct 16 07:21:00 2018 -0700
@@ -25,7 +25,7 @@
   > revisions.disambiguatewithin=not 4
   > EOF
   $ hg l
-  5:0
+  5:00
   4:7ba5d
   3:7b
   2:72