committablefilectx: propagate ancestry info to parent to fix annotation

Before this patch, annotating working directory could include wrong revisions
that were hidden or belonged to different branches. This fixes wfctx.parents()
to set _descendantrev so that all ancestors can take advantage of the linkrev
adjustment introduced at c48924787eaa. _adjustlinkrev() can handle 'None'
revision thanks to 5a12ef618c03.

mercurial/context.py

@@ -1618,7 +1618,7 b' class committablefilectx(basefilectx):'
         for pc in pcl[1:]:
             pl.append((path, filenode(pc, path), fl))
 
-        return [filectx(self._repo, p, fileid=n, filelog=l)
+        return [self._parentfilectx(p, fileid=n, filelog=l)
                 for p, n, l in pl if n != nullid]
 
     def children(self):

tests/test-annotate.t

@@ -556,6 +556,7 b' create history with a filerev whose link'
   grafting 1:fd27c222e3e6 "contentB"
   $ echo C >> a
   $ hg commit -m 'contentC'
+  $ echo W >> a
   $ hg log -G
   @  changeset:   4:072f1e8df249
   |  tag:         tip
@@ -592,6 +593,12 b' Annotate should list ancestor of startin'
   3: B
   4: C
 
+  $ hg annotate a -r 'wdir()'
+  0 : A
+  3 : B
+  4 : C
+  4+: W
+
 Even when the starting revision is the linkrev-shadowed one:
 
   $ hg annotate a -r 3