fileset: matchctx.existing() must consider unknown files

By default, unknown files are ignored. If the 'unknown()' predicate
appears in the syntax tree, then they are taken in account.
Unfortunately, matchctx.existing() was filtering against non-deleted
context files, which does not include unknown files. So:

  $ hg debugfileset 'binary() and unknown()'

would not return existing binary unknown files.

mercurial/fileset.py

@@ -432,10 +432,12 b' class matchctx(object):'
     def existing(self):
         if self._status is not None:
             removed = set(self._status[3])
+            unknown = set(self._status[4])
         else:
             removed = set()
+            unknown = set()
         return (f for f in self.subset
-                if f in self.ctx and f not in removed)
+                if (f in self.ctx and f not in removed) or f in unknown)
     def narrow(self, files):
         return matchctx(self.ctx, self.filter(files), self._status)
 

tests/test-fileset.t

@@ -80,4 +80,9 b' Test files properties'
 
   >>> file('bin', 'wb').write('\0a')
   $ fileset 'binary()'
+  $ fileset 'binary() and unknown()'
+  bin
+  $ hg add bin
+  $ fileset 'binary()'
+  bin