checkheads: upgrade the obsolescence postprocessing logic (issue4354)

The previous logic had many shortcoming (eg: looking at the head only, not
handling prune, etc...), the new logic use a more robust approach:

For each head, we check if after the push all changesets exclusive to this heads
will be obsolete. If they are, the branch considered be "replaced".

To check if a changeset will be obsolete, we simply checks:

* the changeset phase

* the existence of a marker relevant to the "pushed set" that affects the
  changesets..

This fixes two major issues of the previous algorithm:

* branch partially rewritten (eg: head but not root) are no longer detected as
  replaced,

* Prune are now properly handled.

(This implementation was introduction in the evolve extension, version 6.0.0.)

This new algorithm has an extended number of tests, a basic one is provided
in this patch. The others will be introduced in their own changeset for clarity.

In addition, we stop trying to process heads unknown locally, we do not have
enough data to take an informed decision so we should stop pretending we do.
This reflect a test that is now update.

tests/test-push-checkheads-pruned-B1.t

@@ -0,0 +1,72 b''
+====================================
+Testing head checking code: Case B-1
+====================================
+
+Mercurial checks for the introduction of new heads on push. Evolution comes
+into play to detect if existing branches on the server are being replaced by
+some of the new one we push.
+
+This case is part of a series of tests checking this behavior.
+
+Category B: simple case involving pruned changesets
+TestCase 1: single pruned changeset
+
+.. old-state:
+..
+.. * 1 changeset branch
+..
+.. new-state:
+..
+.. * old branch is pruned
+.. * 1 new unrelated branch
+..
+.. expected-result:
+..
+.. * push allowed
+..
+.. graph-summary:
+..
+..       ◔ B
+..       |
+..   A ⊗ |
+..     |/
+..     ●
+
+  $ . $TESTDIR/testlib/push-checkheads-util.sh
+
+Test setup
+----------
+
+  $ mkdir B1
+  $ cd B1
+  $ setuprepos
+  creating basic server and client repo
+  updating to branch default
+  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ cd client
+  $ hg up 0
+  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
+  $ mkcommit B0
+  created new head
+  $ hg debugobsolete --record-parents `getid "desc(A0)"`
+  $ hg log -G --hidden
+  @  74ff5441d343 (draft): B0
+  |
+  | x  8aaa48160adc (draft): A0
+  |/
+  o  1e4be0697311 (public): root
+  
+
+Actual testing
+--------------
+
+  $ hg push
+  pushing to $TESTTMP/B1/server (glob)
+  searching for changes
+  adding changesets
+  adding manifests
+  adding file changes
+  added 1 changesets with 1 changes to 1 files (+1 heads)
+  1 new obsolescence markers
+
+  $ cd ../..

mercurial/discovery.py

@@ -1,450 +1,519 b''
 # discovery.py - protocol changeset discovery functions
 #
 # Copyright 2010 Matt Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 from __future__ import absolute_import
 
+import functools
+
 from .i18n import _
 from .node import (
+    hex,
     nullid,
     short,
 )
 
 from . import (
     bookmarks,
     branchmap,
     error,
-    obsolete,
     phases,
     setdiscovery,
     treediscovery,
     util,
 )
 
 def findcommonincoming(repo, remote, heads=None, force=False):
     """Return a tuple (common, anyincoming, heads) used to identify the common
     subset of nodes between repo and remote.
 
     "common" is a list of (at least) the heads of the common subset.
     "anyincoming" is testable as a boolean indicating if any nodes are missing
       locally. If remote does not support getbundle, this actually is a list of
       roots of the nodes that would be incoming, to be supplied to
       changegroupsubset. No code except for pull should be relying on this fact
       any longer.
     "heads" is either the supplied heads, or else the remote's heads.
 
     If you pass heads and they are all known locally, the response lists just
     these heads in "common" and in "heads".
 
     Please use findcommonoutgoing to compute the set of outgoing nodes to give
     extensions a good hook into outgoing.
     """
 
     if not remote.capable('getbundle'):
         return treediscovery.findcommonincoming(repo, remote, heads, force)
 
     if heads:
         allknown = True
         knownnode = repo.changelog.hasnode # no nodemap until it is filtered
         for h in heads:
             if not knownnode(h):
                 allknown = False
                 break
         if allknown:
             return (heads, False, heads)
 
     res = setdiscovery.findcommonheads(repo.ui, repo, remote,
                                        abortwhenunrelated=not force)
     common, anyinc, srvheads = res
     return (list(common), anyinc, heads or list(srvheads))
 
 class outgoing(object):
     '''Represents the set of nodes present in a local repo but not in a
     (possibly) remote one.
 
     Members:
 
       missing is a list of all nodes present in local but not in remote.
       common is a list of all nodes shared between the two repos.
       excluded is the list of missing changeset that shouldn't be sent remotely.
       missingheads is the list of heads of missing.
       commonheads is the list of heads of common.
 
     The sets are computed on demand from the heads, unless provided upfront
     by discovery.'''
 
     def __init__(self, repo, commonheads=None, missingheads=None,
                  missingroots=None):
         # at least one of them must not be set
         assert None in (commonheads, missingroots)
         cl = repo.changelog
         if missingheads is None:
             missingheads = cl.heads()
         if missingroots:
             discbases = []
             for n in missingroots:
                 discbases.extend([p for p in cl.parents(n) if p != nullid])
             # TODO remove call to nodesbetween.
             # TODO populate attributes on outgoing instance instead of setting
             # discbases.
             csets, roots, heads = cl.nodesbetween(missingroots, missingheads)
             included = set(csets)
             missingheads = heads
             commonheads = [n for n in discbases if n not in included]
         elif not commonheads:
             commonheads = [nullid]
         self.commonheads = commonheads
         self.missingheads = missingheads
         self._revlog = cl
         self._common = None
         self._missing = None
         self.excluded = []
 
     def _computecommonmissing(self):
         sets = self._revlog.findcommonmissing(self.commonheads,
                                               self.missingheads)
         self._common, self._missing = sets
 
     @util.propertycache
     def common(self):
         if self._common is None:
             self._computecommonmissing()
         return self._common
 
     @util.propertycache
     def missing(self):
         if self._missing is None:
             self._computecommonmissing()
         return self._missing
 
 def findcommonoutgoing(repo, other, onlyheads=None, force=False,
                        commoninc=None, portable=False):
     '''Return an outgoing instance to identify the nodes present in repo but
     not in other.
 
     If onlyheads is given, only nodes ancestral to nodes in onlyheads
     (inclusive) are included. If you already know the local repo's heads,
     passing them in onlyheads is faster than letting them be recomputed here.
 
     If commoninc is given, it must be the result of a prior call to
     findcommonincoming(repo, other, force) to avoid recomputing it here.
 
     If portable is given, compute more conservative common and missingheads,
     to make bundles created from the instance more portable.'''
     # declare an empty outgoing object to be filled later
     og = outgoing(repo, None, None)
 
     # get common set if not provided
     if commoninc is None:
         commoninc = findcommonincoming(repo, other, force=force)
     og.commonheads, _any, _hds = commoninc
 
     # compute outgoing
     mayexclude = (repo._phasecache.phaseroots[phases.secret] or repo.obsstore)
     if not mayexclude:
         og.missingheads = onlyheads or repo.heads()
     elif onlyheads is None:
         # use visible heads as it should be cached
         og.missingheads = repo.filtered("served").heads()
         og.excluded = [ctx.node() for ctx in repo.set('secret() or extinct()')]
     else:
         # compute common, missing and exclude secret stuff
         sets = repo.changelog.findcommonmissing(og.commonheads, onlyheads)
         og._common, allmissing = sets
         og._missing = missing = []
         og.excluded = excluded = []
         for node in allmissing:
             ctx = repo[node]
             if ctx.phase() >= phases.secret or ctx.extinct():
                 excluded.append(node)
             else:
                 missing.append(node)
         if len(missing) == len(allmissing):
             missingheads = onlyheads
         else: # update missing heads
             missingheads = phases.newheads(repo, onlyheads, excluded)
         og.missingheads = missingheads
     if portable:
         # recompute common and missingheads as if -r<rev> had been given for
         # each head of missing, and --base <rev> for each head of the proper
         # ancestors of missing
         og._computecommonmissing()
         cl = repo.changelog
         missingrevs = set(cl.rev(n) for n in og._missing)
         og._common = set(cl.ancestors(missingrevs)) - missingrevs
         commonheads = set(og.commonheads)
         og.missingheads = [h for h in og.missingheads if h not in commonheads]
 
     return og
 
 def _headssummary(repo, remote, outgoing):
     """compute a summary of branch and heads status before and after push
 
     return {'branch': ([remoteheads], [newheads], [unsyncedheads])} mapping
 
     - branch: the branch name
     - remoteheads: the list of remote heads known locally
                    None if the branch is new
     - newheads: the new remote heads (known locally) with outgoing pushed
     - unsyncedheads: the list of remote heads unknown locally.
     """
     cl = repo.changelog
     headssum = {}
     # A. Create set of branches involved in the push.
     branches = set(repo[n].branch() for n in outgoing.missing)
     remotemap = remote.branchmap()
     newbranches = branches - set(remotemap)
     branches.difference_update(newbranches)
 
     # A. register remote heads
     remotebranches = set()
     for branch, heads in remote.branchmap().iteritems():
         remotebranches.add(branch)
         known = []
         unsynced = []
         knownnode = cl.hasnode # do not use nodemap until it is filtered
         for h in heads:
             if knownnode(h):
                 known.append(h)
             else:
                 unsynced.append(h)
         headssum[branch] = (known, list(known), unsynced)
     # B. add new branch data
     missingctx = list(repo[n] for n in outgoing.missing)
     touchedbranches = set()
     for ctx in missingctx:
         branch = ctx.branch()
         touchedbranches.add(branch)
         if branch not in headssum:
             headssum[branch] = (None, [], [])
 
     # C drop data about untouched branches:
     for branch in remotebranches - touchedbranches:
         del headssum[branch]
 
     # D. Update newmap with outgoing changes.
     # This will possibly add new heads and remove existing ones.
     newmap = branchmap.branchcache((branch, heads[1])
                                  for branch, heads in headssum.iteritems()
                                  if heads[0] is not None)
     newmap.update(repo, (ctx.rev() for ctx in missingctx))
     for branch, newheads in newmap.iteritems():
         headssum[branch][1][:] = newheads
     return headssum
 
 def _oldheadssummary(repo, remoteheads, outgoing, inc=False):
     """Compute branchmapsummary for repo without branchmap support"""
 
     # 1-4b. old servers: Check for new topological heads.
     # Construct {old,new}map with branch = None (topological branch).
     # (code based on update)
     knownnode = repo.changelog.hasnode # no nodemap until it is filtered
     oldheads = set(h for h in remoteheads if knownnode(h))
     # all nodes in outgoing.missing are children of either:
     # - an element of oldheads
     # - another element of outgoing.missing
     # - nullrev
     # This explains why the new head are very simple to compute.
     r = repo.set('heads(%ln + %ln)', oldheads, outgoing.missing)
     newheads = list(c.node() for c in r)
     # set some unsynced head to issue the "unsynced changes" warning
     if inc:
         unsynced = set([None])
     else:
         unsynced = set()
     return {None: (oldheads, newheads, unsynced)}
 
 def _nowarnheads(pushop):
     # Compute newly pushed bookmarks. We don't warn about bookmarked heads.
     repo = pushop.repo.unfiltered()
     remote = pushop.remote
     localbookmarks = repo._bookmarks
     remotebookmarks = remote.listkeys('bookmarks')
     bookmarkedheads = set()
 
     # internal config: bookmarks.pushing
     newbookmarks = [localbookmarks.expandname(b)
                     for b in pushop.ui.configlist('bookmarks', 'pushing')]
 
     for bm in localbookmarks:
         rnode = remotebookmarks.get(bm)
         if rnode and rnode in repo:
             lctx, rctx = repo[bm], repo[rnode]
             if bookmarks.validdest(repo, rctx, lctx):
                 bookmarkedheads.add(lctx.node())
         else:
             if bm in newbookmarks and bm not in remotebookmarks:
                 bookmarkedheads.add(repo[bm].node())
 
     return bookmarkedheads
 
 def checkheads(pushop):
     """Check that a push won't add any outgoing head
 
     raise Abort error and display ui message as needed.
     """
 
     repo = pushop.repo.unfiltered()
     remote = pushop.remote
     outgoing = pushop.outgoing
     remoteheads = pushop.remoteheads
     newbranch = pushop.newbranch
     inc = bool(pushop.incoming)
 
     # Check for each named branch if we're creating new remote heads.
     # To be a remote head after push, node must be either:
     # - unknown locally
     # - a local outgoing head descended from update
     # - a remote head that's known locally and not
     #   ancestral to an outgoing head
     if remoteheads == [nullid]:
         # remote is empty, nothing to check.
         return
 
     if remote.capable('branchmap'):
         headssum = _headssummary(repo, remote, outgoing)
     else:
         headssum = _oldheadssummary(repo, remoteheads, outgoing, inc)
     newbranches = [branch for branch, heads in headssum.iteritems()
                    if heads[0] is None]
     # 1. Check for new branches on the remote.
     if newbranches and not newbranch:  # new branch requires --new-branch
         branchnames = ', '.join(sorted(newbranches))
         raise error.Abort(_("push creates new remote branches: %s!")
                            % branchnames,
                          hint=_("use 'hg push --new-branch' to create"
                                 " new remote branches"))
 
     # 2. Find heads that we need not warn about
     nowarnheads = _nowarnheads(pushop)
 
     # 3. Check for new heads.
     # If there are more heads after the push than before, a suitable
     # error message, depending on unsynced status, is displayed.
     errormsg = None
     # If there is no obsstore, allfuturecommon won't be used, so no
     # need to compute it.
     if repo.obsstore:
         allmissing = set(outgoing.missing)
         cctx = repo.set('%ld', outgoing.common)
         allfuturecommon = set(c.node() for c in cctx)
         allfuturecommon.update(allmissing)
     for branch, heads in sorted(headssum.iteritems()):
         remoteheads, newheads, unsyncedheads = heads
         candidate_newhs = set(newheads)
         # add unsynced data
         if remoteheads is None:
             oldhs = set()
         else:
             oldhs = set(remoteheads)
         oldhs.update(unsyncedheads)
         candidate_newhs.update(unsyncedheads)
         dhs = None # delta heads, the new heads on branch
         if not repo.obsstore:
             discardedheads = set()
             newhs = candidate_newhs
         else:
             newhs, discardedheads = _postprocessobsolete(pushop,
                                                          allfuturecommon,
                                                          candidate_newhs)
         unsynced = sorted(h for h in unsyncedheads if h not in discardedheads)
         if unsynced:
             if None in unsynced:
                 # old remote, no heads data
                 heads = None
             elif len(unsynced) <= 4 or repo.ui.verbose:
                 heads = ' '.join(short(h) for h in unsynced)
             else:
                 heads = (' '.join(short(h) for h in unsynced[:4]) +
                          ' ' + _("and %s others") % (len(unsynced) - 4))
             if heads is None:
                 repo.ui.status(_("remote has heads that are "
                                  "not known locally\n"))
             elif branch is None:
                 repo.ui.status(_("remote has heads that are "
                                  "not known locally: %s\n") % heads)
             else:
                 repo.ui.status(_("remote has heads on branch '%s' that are "
                                  "not known locally: %s\n") % (branch, heads))
         if remoteheads is None:
             if len(newhs) > 1:
                 dhs = list(newhs)
                 if errormsg is None:
                     errormsg = (_("push creates new branch '%s' "
                                   "with multiple heads") % (branch))
                     hint = _("merge or"
                              " see 'hg help push' for details about"
                              " pushing new heads")
         elif len(newhs) > len(oldhs):
             # remove bookmarked or existing remote heads from the new heads list
             dhs = sorted(newhs - nowarnheads - oldhs)
         if dhs:
             if errormsg is None:
                 if branch not in ('default', None):
                     errormsg = _("push creates new remote head %s "
                                  "on branch '%s'!") % (short(dhs[0]), branch)
                 elif repo[dhs[0]].bookmarks():
                     errormsg = _("push creates new remote head %s "
                                  "with bookmark '%s'!") % (
                                  short(dhs[0]), repo[dhs[0]].bookmarks()[0])
                 else:
                     errormsg = _("push creates new remote head %s!"
                                  ) % short(dhs[0])
                 if unsyncedheads:
                     hint = _("pull and merge or"
                              " see 'hg help push' for details about"
                              " pushing new heads")
                 else:
                     hint = _("merge or"
                              " see 'hg help push' for details about"
                              " pushing new heads")
             if branch is None:
                 repo.ui.note(_("new remote heads:\n"))
             else:
                 repo.ui.note(_("new remote heads on branch '%s':\n") % branch)
             for h in dhs:
                 repo.ui.note((" %s\n") % short(h))
     if errormsg:
         raise error.Abort(errormsg, hint=hint)
 
 def _postprocessobsolete(pushop, futurecommon, candidate_newhs):
     """post process the list of new heads with obsolescence information
 
-    Exists as a subfunction to contain the complexity and allow extensions to
+    Exists as a sub-function to contain the complexity and allow extensions to
     experiment with smarter logic.
+
     Returns (newheads, discarded_heads) tuple
     """
-    # remove future heads which are actually obsoleted by another
-    # pushed element:
+    # known issue
     #
-    # XXX as above, There are several cases this code does not handle
-    # XXX properly
-    #
-    # (1) if <nh> is public, it won't be affected by obsolete marker
-    #     and a new is created
+    # * We "silently" skip processing on all changeset unknown locally
     #
-    # (2) if the new heads have ancestors which are not obsolete and
-    #     not ancestors of any other heads we will have a new head too.
-    #
-    # These two cases will be easy to handle for known changeset but
-    # much more tricky for unsynced changes.
-    #
-    # In addition, this code is confused by prune as it only looks for
-    # successors of the heads (none if pruned) leading to issue4354
+    # * if <nh> is public on the remote, it won't be affected by obsolete
+    #     marker and a new is created
+
+    # define various utilities and containers
     repo = pushop.repo
-    newhs = set()
-    discarded = set()
-    for nh in candidate_newhs:
-        if nh in repo and repo[nh].phase() <= phases.public:
+    unfi = repo.unfiltered()
+    tonode = unfi.changelog.node
+    public = phases.public
+    getphase = unfi._phasecache.phase
+    ispublic = (lambda r: getphase(unfi, r) == public)
+    hasoutmarker = functools.partial(pushingmarkerfor, unfi.obsstore,
+                                     futurecommon)
+    successorsmarkers = unfi.obsstore.successors
+    newhs = set() # final set of new heads
+    discarded = set() # new head of fully replaced branch
+
+    localcandidate = set() # candidate heads known locally
+    unknownheads = set() # candidate heads unknown locally
+    for h in candidate_newhs:
+        if h in unfi:
+            localcandidate.add(h)
+        else:
+            if successorsmarkers.get(h) is not None:
+                msg = ('checkheads: remote head unknown locally has'
+                       ' local marker: %s\n')
+                repo.ui.debug(msg % hex(h))
+            unknownheads.add(h)
+
+    # fast path the simple case
+    if len(localcandidate) == 1:
+        return unknownheads | set(candidate_newhs), set()
+
+    # actually process branch replacement
+    while localcandidate:
+        nh = localcandidate.pop()
+        # run this check early to skip the evaluation of the whole branch
+        if (nh in futurecommon
+                or unfi[nh].phase() <= public):
+            newhs.add(nh)
+            continue
+
+        # Get all revs/nodes on the branch exclusive to this head
+        # (already filtered heads are "ignored"))
+        branchrevs = unfi.revs('only(%n, (%ln+%ln))',
+                               nh, localcandidate, newhs)
+        branchnodes = [tonode(r) for r in branchrevs]
+
+        # The branch won't be hidden on the remote if
+        # * any part of it is public,
+        # * 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(not hasoutmarker(n) for n in branchnodes)):
             newhs.add(nh)
         else:
-            for suc in obsolete.allsuccessors(repo.obsstore, [nh]):
-                if suc != nh and suc in futurecommon:
-                    discarded.add(nh)
-                    break
-            else:
-                newhs.add(nh)
+            # note: there is a corner case if there is a merge in the branch.
+            # we might end up with -more- heads.  However, these heads are not
+            # "added" by the push, but more by the "removal" on the remote so I
+            # think is a okay to ignore them,
+            discarded.add(nh)
+    newhs |= unknownheads
     return newhs, discarded
+
+def pushingmarkerfor(obsstore, pushset, node):
+    """true if some markers are to be pushed for node
+
+    We cannot just look in to the pushed obsmarkers from the pushop because
+    discovery might have filtered relevant markers. In addition listing all
+    markers relevant to all changesets in the pushed set would be too expensive
+    (O(len(repo)))
+
+    (note: There are cache opportunity in this function. but it would requires
+    a two dimensional stack.)
+    """
+    successorsmarkers = obsstore.successors
+    stack = [node]
+    seen = set(stack)
+    while stack:
+        current = stack.pop()
+        if current in pushset:
+            return True
+        markers = successorsmarkers.get(current, ())
+        # markers fields = ('prec', 'succs', 'flag', 'meta', 'date', 'parents')
+        for m in markers:
+            nexts = m[1] # successors
+            if not nexts: # this is a prune marker
+                nexts = m[5] # parents
+            for n in nexts:
+                if n not in seen:
+                    seen.add(n)
+                    stack.append(n)
+    return False

tests/test-obsolete-checkheads.t

@@ -1,265 +1,283 b''
 Check that obsolete properly strip heads
   $ cat >> $HGRCPATH << EOF
   > [phases]
   > # public changeset are not obsolete
   > publish=false
   > [ui]
   > logtemplate='{node|short} ({phase}) {desc|firstline}\n'
   > [experimental]
   > evolution=createmarkers
   > EOF
   $ mkcommit() {
   >    echo "$1" > "$1"
   >    hg add "$1"
   >    hg ci -m "add $1"
   > }
   $ getid() {
   >    hg id --debug -ir "desc('$1')"
   > }
 
 
   $ hg init remote
   $ cd remote
   $ mkcommit base
   $ hg phase --public .
   $ cd ..
   $ cp -R remote base
   $ hg clone remote local
   updating to branch default
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ cd local
 
 New head replaces old head
 ==========================
 
 setup
 (we add the 1 flags to prevent bumped error during the test)
 
   $ mkcommit old
   $ hg push
   pushing to $TESTTMP/remote (glob)
   searching for changes
   adding changesets
   adding manifests
   adding file changes
   added 1 changesets with 1 changes to 1 files
   $ hg up -q '.^'
   $ mkcommit new
   created new head
   $ hg debugobsolete --flags 1 `getid old` `getid new`
   $ hg log -G --hidden
   @  71e3228bffe1 (draft) add new
   |
   | x  c70b08862e08 (draft) add old
   |/
   o  b4952fcf48cf (public) add base
   
   $ cp -R ../remote ../backup1
 
 old exists remotely as draft. It is obsoleted by new that we now push.
 Push should not warn about creating new head
 
   $ hg push
   pushing to $TESTTMP/remote (glob)
   searching for changes
   adding changesets
   adding manifests
   adding file changes
   added 1 changesets with 1 changes to 1 files (+1 heads)
 
 old head is now public (public local version)
 =============================================
 
 setup
 
   $ rm -fr ../remote
   $ cp -R ../backup1 ../remote
   $ hg -R ../remote phase --public c70b08862e08
   $ hg pull -v
   pulling from $TESTTMP/remote (glob)
   searching for changes
   no changes found
   $ hg log -G --hidden
   @  71e3228bffe1 (draft) add new
   |
   | o  c70b08862e08 (public) add old
   |/
   o  b4952fcf48cf (public) add base
   
 
 Abort: old will still be an head because it's public.
 
   $ hg push
   pushing to $TESTTMP/remote (glob)
   searching for changes
   abort: push creates new remote head 71e3228bffe1!
   (merge or see 'hg help push' for details about pushing new heads)
   [255]
 
 old head is now public (public remote version)
 ==============================================
 
 TODO: Not implemented yet.
 
 # setup
 #
 #   $ rm -fr ../remote
 #   $ cp -R ../backup1 ../remote
 #   $ hg -R ../remote phase --public c70b08862e08
 #   $ hg phase --draft --force c70b08862e08
 #   $ hg log -G --hidden
 #   @  71e3228bffe1 (draft) add new
 #   |
 #   | x  c70b08862e08 (draft) add old
 #   |/
 #   o  b4952fcf48cf (public) add base
 #
 #
 #
 # Abort: old will still be an head because it's public.
 #
 #   $ hg push
 #   pushing to $TESTTMP/remote
 #   searching for changes
 #   abort: push creates new remote head 71e3228bffe1!
 #   (merge or see 'hg help push' for details about pushing new heads)
 #   [255]
 
 old head is obsolete but replacement is not pushed
 ==================================================
 
 setup
 
   $ rm -fr ../remote
   $ cp -R ../backup1 ../remote
   $ hg phase --draft --force '(0::) - 0'
   $ hg up -q '.^'
   $ mkcommit other
   created new head
   $ hg log -G --hidden
   @  d7d41ccbd4de (draft) add other
   |
   | o  71e3228bffe1 (draft) add new
   |/
   | x  c70b08862e08 (draft) add old
   |/
   o  b4952fcf48cf (public) add base
   
 
 old exists remotely as draft. It is obsoleted by new but we don't push new.
 Push should abort on new head
 
   $ hg push -r 'desc("other")'
   pushing to $TESTTMP/remote (glob)
   searching for changes
   abort: push creates new remote head d7d41ccbd4de!
   (merge or see 'hg help push' for details about pushing new heads)
   [255]
 
 
 
 Both precursors and successors are already know remotely. Descendant adds heads
 ===============================================================================
 
 setup. (The obsolete marker is known locally only
 
   $ cd ..
   $ rm -rf local
   $ hg clone remote local
   updating to branch default
   2 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ cd local
   $ mkcommit old
   old already tracked!
   nothing changed
   [1]
   $ hg up -q '.^'
   $ mkcommit new
   created new head
   $ hg push -f
   pushing to $TESTTMP/remote (glob)
   searching for changes
   adding changesets
   adding manifests
   adding file changes
   added 1 changesets with 1 changes to 1 files (+1 heads)
   $ mkcommit desc1
   $ hg up -q '.^'
   $ mkcommit desc2
   created new head
   $ hg debugobsolete `getid old` `getid new`
   $ hg log -G --hidden
   @  5fe37041cc2b (draft) add desc2
   |
   | o  a3ef1d111c5f (draft) add desc1
   |/
   o  71e3228bffe1 (draft) add new
   |
   | x  c70b08862e08 (draft) add old
   |/
   o  b4952fcf48cf (public) add base
   
   $ hg log -G --hidden -R ../remote
   o  71e3228bffe1 (draft) add new
   |
   | o  c70b08862e08 (draft) add old
   |/
   @  b4952fcf48cf (public) add base
   
   $ cp -R ../remote ../backup2
 
 Push should not warn about adding new heads. We create one, but we'll delete
 one anyway.
 
   $ hg push
   pushing to $TESTTMP/remote (glob)
   searching for changes
   adding changesets
   adding manifests
   adding file changes
   added 2 changesets with 2 changes to 2 files (+1 heads)
 
 
 Remote head is unknown but obsoleted by a local changeset
 =========================================================
 
 setup
 
   $ rm -fr ../remote
   $ cp -R ../backup1 ../remote
   $ cd ..
   $ rm -rf local
   $ hg clone remote local -r 0
   adding changesets
   adding manifests
   adding file changes
   added 1 changesets with 1 changes to 1 files
   updating to branch default
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ cd local
   $ mkcommit new
   $ hg -R ../remote id --debug -r tip
   c70b08862e0838ea6d7c59c85da2f1ed6c8d67da tip
   $ hg  id --debug -r tip
   71e3228bffe1886550777233d6c97bb5a6b2a650 tip
   $ hg debugobsolete c70b08862e0838ea6d7c59c85da2f1ed6c8d67da 71e3228bffe1886550777233d6c97bb5a6b2a650
   $ hg log -G --hidden
   @  71e3228bffe1 (draft) add new
   |
   o  b4952fcf48cf (public) add base
   
   $ hg log -G --hidden -R ../remote
   o  c70b08862e08 (draft) add old
   |
   @  b4952fcf48cf (public) add base
   
 
-Push should not complain about new heads.
+We do not have enought data to take the right decision, we should fail
+
+  $ hg push
+  pushing to $TESTTMP/remote (glob)
+  searching for changes
+  remote has heads on branch 'default' that are not known locally: c70b08862e08
+  abort: push creates new remote head 71e3228bffe1!
+  (pull and merge or see 'hg help push' for details about pushing new heads)
+  [255]
 
-  $ hg push --traceback
+Pulling the missing data makes it work
+
+  $ hg pull
+  pulling from $TESTTMP/remote (glob)
+  searching for changes
+  adding changesets
+  adding manifests
+  adding file changes
+  added 1 changesets with 1 changes to 1 files (+1 heads)
+  (run 'hg heads' to see heads)
+  $ hg push
   pushing to $TESTTMP/remote (glob)
   searching for changes
   adding changesets
   adding manifests
   adding file changes
   added 1 changesets with 1 changes to 1 files (+1 heads)