diff --git a/mercurial/configitems.py b/mercurial/configitems.py
--- a/mercurial/configitems.py
+++ b/mercurial/configitems.py
@@ -590,6 +590,11 @@ coreconfigitem(
 coreconfigitem(
     b'experimental', b'maxdeltachainspan', default=-1,
 )
+# tracks files which were undeleted (merge might delete them but we explicitly
+# kept/undeleted them) and creates new filenodes for them
+coreconfigitem(
+    b'experimental', b'merge-track-salvaged', default=False,
+)
 coreconfigitem(
     b'experimental', b'mergetempdirprefix', default=None,
 )
diff --git a/tests/test-merge-criss-cross.t b/tests/test-merge-criss-cross.t
--- a/tests/test-merge-criss-cross.t
+++ b/tests/test-merge-criss-cross.t
@@ -1,3 +1,15 @@
+#testcases old newfilenode
+
+#if newfilenode
+Enable the config option
+------------------------
+
+  $ cat >> $HGRCPATH <<EOF
+  > [experimental]
+  > merge-track-salvaged = True
+  > EOF
+#endif
+
 Criss cross merging
 
   $ hg init criss-cross