fileset: fix generator vs list bug in fast path

  $ hg debugfileset 'a or b'

would only return a or b but not both because the base file list was a
generator instead of a replayable sequence.

mercurial/fileset.py

@@ -485,7 +485,7 b' def getfileset(ctx, expr):'
             subset.extend(c)
     else:
         status = None
-        subset = ctx.walk(ctx.match([]))
+        subset = list(ctx.walk(ctx.match([])))
 
     return getset(matchctx(ctx, subset, status), tree)
 

tests/test-cat.t

@@ -21,3 +21,14 b''
   [1]
   $ hg cat -r 1 b
   1
+
+Test fileset
+
+  $ echo 3 > c
+  $ hg ci -Am addmore c
+  $ hg cat 'set:not(b) or a'
+  3
+  $ hg cat 'set:c or b'
+  1
+  3
+

tests/test-fileset.t

@@ -222,4 +222,7 b' Test with a revision'
   sub
   $ fileset -r4 'subrepo("sub")'
   sub
+  $ fileset -r4 'b2 or c1'
+  b2
+  c1