diff -r 7edd4ceefce0 -r ce4018f03520 hgext3rd/evolve/legacy.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/hgext3rd/evolve/legacy.py	Tue Nov 01 16:18:21 2016 +0100
@@ -0,0 +1,163 @@
+# Copyright 2011 Pierre-Yves David <pierre-yves.david@ens-lyon.org>
+#                Logilab SA        <contact@logilab.fr>
+#
+# This software may be used and distributed according to the terms of the
+# GNU General Public License version 2 or any later version.
+"""Deprecated extension that formerly introduced "Changeset Obsolescence".
+
+This concept is now partially in Mercurial core (starting with Mercurial 2.3).
+The remaining logic has been grouped with the evolve extension.
+
+Some code remains in this extensions to detect and convert prehistoric format
+of obsolete marker than early user may have create. Keep it enabled if you
+were such user.
+"""
+
+from mercurial import error
+
+try:
+    from mercurial import obsolete
+except ImportError:
+    raise error.Abort('Obsolete extension requires Mercurial 2.3 (or later)')
+
+import sys
+import json
+
+from mercurial import cmdutil
+from mercurial.i18n import _
+from mercurial.node import bin, nullid
+from mercurial import util
+
+
+#####################################################################
+### Older format management                                       ###
+#####################################################################
+
+# Code related to detection and management of older legacy format never
+# handled by core
+
+
+def reposetup(ui, repo):
+    """Detect that a repo still contains some old obsolete format
+    """
+    if not repo.local():
+        return
+    evolveopts = ui.configlist('experimental', 'evolution')
+    if not evolveopts:
+        evolveopts = 'all'
+        ui.setconfig('experimental', 'evolution', evolveopts)
+    for arg in sys.argv:
+        if 'debugc' in arg:
+            break
+    else:
+        data = repo.opener.tryread('obsolete-relations')
+        if not data:
+            data = repo.svfs.tryread('obsoletemarkers')
+        if data:
+            raise error.Abort('old format of obsolete marker detected!\n'
+                              'run `hg debugconvertobsolete` once.')
+
+def _obsdeserialize(flike):
+    """read a file like object serialized with _obsserialize
+
+    this deserialize into a {subject -> objects} mapping
+
+    this was the very first format ever."""
+    rels = {}
+    for line in flike:
+        subhex, objhex = line.split()
+        subnode = bin(subhex)
+        if subnode == nullid:
+            subnode = None
+        rels.setdefault(subnode, set()).add(bin(objhex))
+    return rels
+
+cmdtable = {}
+command = cmdutil.command(cmdtable)
+@command('debugconvertobsolete', [], '')
+def cmddebugconvertobsolete(ui, repo):
+    """import markers from an .hg/obsolete-relations file"""
+    cnt = 0
+    err = 0
+    l = repo.lock()
+    some = False
+    try:
+        unlink = []
+        tr = repo.transaction('convert-obsolete')
+        try:
+            repo._importoldobsolete = True
+            store = repo.obsstore
+            ### very first format
+            try:
+                f = repo.opener('obsolete-relations')
+                try:
+                    some = True
+                    for line in f:
+                        subhex, objhex = line.split()
+                        suc = bin(subhex)
+                        prec = bin(objhex)
+                        sucs = (suc==nullid) and [] or [suc]
+                        meta = {
+                            'date':  '%i %i' % util.makedate(),
+                            'user': ui.username(),
+                            }
+                        try:
+                            store.create(tr, prec, sucs, 0, metadata=meta)
+                            cnt += 1
+                        except ValueError:
+                            repo.ui.write_err("invalid old marker line: %s"
+                                              % (line))
+                            err += 1
+                finally:
+                    f.close()
+                unlink.append(repo.join('obsolete-relations'))
+            except IOError:
+                pass
+            ### second (json) format
+            data = repo.svfs.tryread('obsoletemarkers')
+            if data:
+                some = True
+                for oldmark in json.loads(data):
+                    del oldmark['id']  # dropped for now
+                    del oldmark['reason']  # unused until then
+                    oldobject = str(oldmark.pop('object'))
+                    oldsubjects = [str(s) for s in oldmark.pop('subjects', [])]
+                    LOOKUP_ERRORS = (error.RepoLookupError, error.LookupError)
+                    if len(oldobject) != 40:
+                        try:
+                            oldobject = repo[oldobject].node()
+                        except LOOKUP_ERRORS:
+                            pass
+                    if any(len(s) != 40 for s in oldsubjects):
+                        try:
+                            oldsubjects = [repo[s].node() for s in oldsubjects]
+                        except LOOKUP_ERRORS:
+                            pass
+
+                    oldmark['date'] = '%i %i' % tuple(oldmark['date'])
+                    meta = dict((k.encode('utf-8'), v.encode('utf-8'))
+                                 for k, v in oldmark.iteritems())
+                    try:
+                        succs = [bin(n) for n in oldsubjects]
+                        succs = [n for n in succs if n != nullid]
+                        store.create(tr, bin(oldobject), succs,
+                                     0, metadata=meta)
+                        cnt += 1
+                    except ValueError:
+                        repo.ui.write_err("invalid marker %s -> %s\n"
+                                     % (oldobject, oldsubjects))
+                        err += 1
+                unlink.append(repo.sjoin('obsoletemarkers'))
+            tr.close()
+            for path in unlink:
+                util.unlink(path)
+        finally:
+            tr.release()
+    finally:
+        del repo._importoldobsolete
+        l.release()
+    if not some:
+        ui.warn(_('nothing to do\n'))
+    ui.status('%i obsolete marker converted\n' % cnt)
+    if err:
+        ui.write_err('%i conversion failed. check you graph!\n' % err)