diff -r c3f6e97c71b1 -r 4140d680784e hgext/evolve.py
--- a/hgext/evolve.py	Tue Jun 30 18:32:12 2015 -0700
+++ b/hgext/evolve.py	Thu Jun 25 13:33:50 2015 -0700
@@ -2137,6 +2137,8 @@
      ('r', 'rev', [], _("revisions to prune")),
      ('k', 'keep', None, _("does not modify working copy during prune")),
      ('', 'biject', False, _("do a 1-1 map between rev and successor ranges")),
+     ('', 'fold', False, _("record a fold (multiple precursors, one successors)")),
+     ('', 'split', False, _("record a split (on precursor, multiple successors)")),
      ('B', 'bookmark', '', _("remove revs only reachable from given"
                              " bookmark"))] + metadataopts,
     _('[OPTION] [-r] REV...'))
@@ -2159,12 +2161,22 @@
     revisions to prune and successor changesets. This option may be removed in
     a future release (with the functionality absorbed automatically).
 
+    If you specify multiple revisions in --succ, you are recording a "split"
+    and have to acknowledge it by usng --split. The same logic apply when you
+    prune multiple changesets with a single successors, this will record a
+    "fold" requires a --fold flag.
     """
     revs = scmutil.revrange(repo, list(revs) + opts.get('rev'))
     succs = opts['new'] + opts['succ']
     bookmark = opts.get('bookmark')
     metadata = _getmetadata(**opts)
     biject = opts.get('biject')
+    fold = opts.get('fold')
+    split = opts.get('split')
+
+    options = [o for o in ('biject', 'fold', 'split') if opts.get(o)]
+    if 1 < len(options):
+        raise util.Abort(_("can only specify one of %s") % ', '.join(options))
 
     if bookmark:
         marks,revs = _reachablefrombookmark(repo, revs, bookmark)
@@ -2204,15 +2216,20 @@
         if not biject and len(sucs) > 1 and len(precs) > 1:
             msg = "Can't use multiple successors for multiple precursors"
             raise util.Abort(msg)
-
-        if biject and len(sucs) != len(precs):
+        elif biject and len(sucs) != len(precs):
             msg = "Can't use %d successors for %d precursors" \
                 % (len(sucs), len(precs))
             raise util.Abort(msg)
-
-        relations = [(p, sucs) for p in precs]
-        if biject:
+        elif (len(precs) == 1 and len(sucs) > 1) and not split:
+            msg = "please add --split if you want to do a split"
+            raise util.Abort(msg)
+        elif len(sucs) == 1 and len(precs) > 1 and not fold:
+            msg = "please add --fold if you want to do a fold"
+            raise util.Abort(msg)
+        elif biject:
             relations = [(p, (s,)) for p, s in zip(precs, sucs)]
+        else:
+            relations = [(p, sucs) for p in precs]
 
         wdp = repo['.']