revset: use integer representation of wdir() in revset

This is the simplest way to handle wdir() revision in revset. None didn't
work well because revset heavily depends on integer operations such as min(),
max(), sorted(), x:y, etc.

One downside is that we cannot do "wctx.rev() in set" because wctx.rev() is
still None. We could wrap the result set by wdirproxyset that translates None
to wdirrev, but it seems overengineered at this point.

    result = getset(repo, subset, tree)
    if 'wdir' in funcsused(tree):
        result = wdirproxyset(result)

Test cases need the '(all() + wdir()) &' hack because we have yet to fix the
bootstrapping issue of null and wdir.

mercurial/revset.py

@@ -1481,7 +1481,7 b' def parents(repo, subset, x):'
         up = ps.update
         parentrevs = cl.parentrevs
         for r in getset(repo, fullreposet(repo), x):
-            if r is None:
+            if r == node.wdirrev:
                 up(p.rev() for p in repo[r].parents())
             else:
                 up(parentrevs(r))
@@ -1986,8 +1986,8 b' def user(repo, subset, x):'
 def wdir(repo, subset, x):
     # i18n: "wdir" is a keyword
     getargs(x, 0, 0, _("wdir takes no arguments"))
-    if None in subset or isinstance(subset, fullreposet):
-        return baseset([None])
+    if node.wdirrev in subset or isinstance(subset, fullreposet):
+        return baseset([node.wdirrev])
     return baseset()
 
 # for internal use

tests/test-glog.t

@@ -2392,4 +2392,12 b' should not draw line down to null due to'
      summary:     add a
   
 
+working-directory revision
+
+  $ hg log -G -qr '. + wdir()'
+  o  2147483647:ffffffffffff
+  |
+  @  3:5918b8d165d1
+  |
+
   $ cd ..

tests/test-revset.t

@@ -721,11 +721,19 b" BROKEN: should be '-1'"
 
 Test working-directory revision
   $ hg debugrevspec 'wdir()'
-  None
+  2147483647
   $ hg debugrevspec 'tip or wdir()'
   9
-  None
+  2147483647
   $ hg debugrevspec '0:tip and wdir()'
+  $ log '(all() + wdir()) & min(. + wdir())'
+  9
+  $ log '(all() + wdir()) & max(. + wdir())'
+  2147483647
+  $ log '(all() + wdir()) & first(wdir() + .)'
+  2147483647
+  $ log '(all() + wdir()) & last(. + wdir())'
+  2147483647
 
   $ log 'outgoing()'
   8