templater: shorten pure integers

Originally, the addition of the 'shorten' template function in 9c6b86dd2ed2
would not consider pure integers for shortening. This patch considers two
simple cases: when the integer starts with zero (which is parsed by Mercurial
as a hash first) and when the integer is larger than the tip (obviously not a
rev).

mercurial/templater.py

@@ -416,7 +416,12 b' def shortest(context, mapping, args):'
                     return False
 
             try:
-                int(test)
+                i = int(test)
+                # if we are a pure int, then starting with zero will not be
+                # confused as a rev; or, obviously, if the int is larger than
+                # the value of the tip rev
+                if test[0] == '0' or i > len(cl):
+                    return True
                 return False
             except ValueError:
                 return True