revset: have rev() drop out-of-range or filtered rev explicitly (issue4396)

The recent optimization of "and" operation relies on the assumption that
the rhs set does not contain invalid revisions.  So rev() has to remove
invalid revisions.

This is still faster than using `.filter(lambda r: r == l)`.

revset  #0: rev(25)
0) wall 0.026341 comb 0.020000 user 0.020000 sys 0.000000 (best of 113)
1) wall 0.000038 comb 0.000000 user 0.000000 sys 0.000000 (best of 66567)
2) wall 0.000062 comb 0.000000 user 0.000000 sys 0.000000 (best of 43699)
(0: bbf4f3dfd700^, 1: 3.2-rc, 2: this patch)

mercurial/revset.py

@@ -1351,6 +1351,8 b' def rev(repo, subset, x):'
     except (TypeError, ValueError):
         # i18n: "rev" is a keyword
         raise error.ParseError(_("rev expects a number"))
+    if l not in repo.changelog:
+        return baseset()
     return subset & baseset([l])
 
 def matching(repo, subset, x):

tests/test-obsolete.t

@@ -185,6 +185,8 b' check that various commands work well wi'
   abort: hidden revision '4'!
   (use --hidden to access hidden revisions)
   [255]
+  $ hg debugrevspec 'rev(6)'
+  $ hg debugrevspec 'rev(4)'
 
 Check that public changeset are not accounted as obsolete:
 

tests/test-revset.t

@@ -437,6 +437,18 b' Test empty set input'
   4
   8
   9
+
+Test explicit numeric revision
+  $ log 'rev(-1)'
+  $ log 'rev(0)'
+  0
+  $ log 'rev(9)'
+  9
+  $ log 'rev(10)'
+  $ log 'rev(tip)'
+  hg: parse error: rev expects a number
+  [255]
+
   $ log 'outgoing()'
   8
   9