shortest: use 'x' prefix to disambiguate from revnum if configured

Differential Revision: https://phab.mercurial-scm.org/D4042

mercurial/scmutil.py

@@ -490,6 +490,12 b' def shortesthexnodeidprefix(repo, node, '
 
     def disambiguate(prefix):
         """Disambiguate against revnums."""
+        if repo.ui.configbool('experimental', 'revisions.prefixhexnode'):
+            if mayberevnum(repo, prefix):
+                return 'x' + prefix
+            else:
+                return prefix
+
         hexnode = hex(node)
         for length in range(len(prefix), len(hexnode) + 1):
             prefix = hexnode[:length]

tests/test-template-functions.t

@@ -892,6 +892,11 b' Test shortest(node) with the repo having'
   $ hg log -r 4 -T '{rev}:{shortest(node, 0)}\n' --hidden
   4:107
 
+  $ hg --config experimental.revisions.prefixhexnode=yes log -r 4 -T '{rev}:{shortest(node, 0)}\n'
+  4:x10
+  $ hg --config experimental.revisions.prefixhexnode=yes log -r 4 -T '{rev}:{shortest(node, 0)}\n' --hidden
+  4:x10
+
  node 'c562' should be unique if the other 'c562' nodes are hidden
  (but we don't try the slow path to filter out hidden nodes for now)