diff -r 5f1d0cff514d -r e6ba7e324015 hgext3rd/evolve/evolvecmd.py
--- a/hgext3rd/evolve/evolvecmd.py	Tue Jan 29 20:45:14 2019 +0800
+++ b/hgext3rd/evolve/evolvecmd.py	Sun Jan 13 19:33:19 2019 +0530
@@ -18,6 +18,7 @@
     context,
     copies,
     error,
+    encoding,
     hg,
     merge,
     mergeutil,
@@ -579,6 +580,46 @@
     finally:
         repo.ui.restoreconfig(emtpycommitallowed)
 
+def bypassphase(repo, relation, flag=0, metadata=None, operation='evolve'):
+    """function to create a single obsmarker relation even for public csets
+    where relation should be a single pair (prec, succ)"""
+
+    # prepare metadata
+    if metadata is None:
+        metadata = {}
+    if 'user' not in metadata:
+        luser = repo.ui.config('devel', 'user.obsmarker') or repo.ui.username()
+        metadata['user'] = encoding.fromlocal(luser)
+    # Operation metadata handling
+    useoperation = repo.ui.configbool('experimental',
+                                      'evolution.track-operation')
+    if useoperation and operation:
+        metadata['operation'] = operation
+
+    # Effect flag metadata handling
+    saveeffectflag = repo.ui.configbool('experimental',
+                                        'evolution.effect-flags')
+    with repo.transaction('add-obsolescence-marker') as tr:
+        prec, succ = relation
+        nprec = prec.node()
+        npare = None
+        nsucs = [succ.node()]
+        if not nsucs:
+            npare = tuple(p.node() for p in prec.parents())
+        if nprec in nsucs:
+            raise error.Abort(_("changeset %s cannot obsolete itself") % prec)
+
+        if saveeffectflag:
+            # The effect flag is saved in a versioned field name for
+            # future evolution
+            effectflag = obsutil.geteffectflag(prec, (succ,))
+            metadata[obsutil.EFFECTFLAGFIELD] = "%d" % effectflag
+
+        # create markers
+        repo.obsstore.create(tr, nprec, nsucs, flag, parents=npare,
+                             metadata=metadata, ui=repo.ui)
+        repo.filteredrevcache.clear()
+
 def dirstatedance(repo, oldparent, newparent, match):
     """utility function to fix the dirstate when we change parents from
     oldparent to newparent with a directory working directory using