templater: evaluate each item of revset() as integer revision

Because templater.revset() returns a list of strings, repo["-1"] was mapped to
the tipmost revision. Ideally, we should make revset() return a list of integer
revisions, but it turned out not simple. If revset() is a list of integers,
"{ifcontains(rev, revset(), ...)}" would fail because "ifcontains" casts "rev"
to a string.

So this patch just converts a string back to an integer revision.

mercurial/templatekw.py

@@ -492,7 +492,7 b' def showrevslist(name, revs, **args):'
     repo = args['ctx'].repo()
     f = _showlist(name, revs, **args)
     return _hybrid(f, revs,
-                   lambda x: {name: x, 'ctx': repo[x], 'revcache': {}})
+                   lambda x: {name: x, 'ctx': repo[int(x)], 'revcache': {}})
 
 def showsubrepos(**args):
     """:subrepos: List of strings. Updated subrepositories in the changeset."""

tests/test-command-template.t

@@ -3310,6 +3310,13 b' Test revset function'
   0 a
   p 
 
+a revset item must be evaluated as an integer revision, not an offset from tip
+
+  $ hg log -l 1 -T '{revset("null") % "{rev}:{node|short}"}\n'
+  -1:000000000000
+  $ hg log -l 1 -T '{revset("%s", "null") % "{rev}:{node|short}"}\n'
+  -1:000000000000
+
 Test active bookmark templating
 
   $ hg book foo