checkheads: use "revnum" in the "allfuturecommon" set

The obsolete post-processing needs to know the extend of the pushed set. The
way it is implemented is... suboptimal. It build a full set of all nodes in the
pushset and it does so using changectx. We have much better API for this now.
The simplest is to use the existing lazy ancestors computation. That logic uses
revnum and not node (for good reason) so we start with updating the
post-processing code to handle a "allfuturecommon" set containing revision
numbers.

mercurial/discovery.py

@@ -250,8 +250,9 b' def _headssummary(pushop):'
     if repo.obsstore:
         allmissing = set(outgoing.missing)
         cctx = repo.set('%ld', outgoing.common)
-        allfuturecommon = set(c.node() for c in cctx)
-        allfuturecommon.update(allmissing)
+        allfuturecommon = set(c.rev() for c in cctx)
+        torev = repo.changelog.rev
+        allfuturecommon.update(torev(m) for m in allmissing)
         for branch, heads in sorted(headssum.iteritems()):
             remoteheads, newheads, unsyncedheads, placeholder = heads
             result = _postprocessobsolete(pushop, allfuturecommon, newheads)
@@ -443,7 +444,7 b' def _postprocessobsolete(pushop, futurec'
     public = phases.public
     getphase = unfi._phasecache.phase
     ispublic = (lambda r: getphase(unfi, r) == public)
-    ispushed = (lambda n: n in futurecommon)
+    ispushed = (lambda n: torev(n) in futurecommon)
     hasoutmarker = functools.partial(pushingmarkerfor, unfi.obsstore, ispushed)
     successorsmarkers = unfi.obsstore.successors
     newhs = set() # final set of new heads
@@ -469,7 +470,7 b' def _postprocessobsolete(pushop, futurec'
     while localcandidate:
         nh = localcandidate.pop()
         # run this check early to skip the evaluation of the whole branch
-        if (nh in futurecommon or ispublic(torev(nh))):
+        if (torev(nh) in futurecommon or ispublic(torev(nh))):
             newhs.add(nh)
             continue
 
@@ -484,7 +485,7 b' def _postprocessobsolete(pushop, futurec'
         # * any part of it is considered part of the result by previous logic,
         # * if we have no markers to push to obsolete it.
         if (any(ispublic(r) for r in branchrevs)
-                or any(n in futurecommon for n in branchnodes)
+                or any(torev(n) in futurecommon for n in branchnodes)
                 or any(not hasoutmarker(n) for n in branchnodes)):
             newhs.add(nh)
         else: