diff -r ecc1387138ba -r 50e20154cb68 mercurial/filemerge.py
--- a/mercurial/filemerge.py	Fri Jul 18 21:49:52 2014 -0500
+++ b/mercurial/filemerge.py	Thu Jun 26 01:20:25 2014 +0200
@@ -9,6 +9,7 @@
 from i18n import _
 import util, simplemerge, match, error, templater, templatekw
 import os, tempfile, re, filecmp
+import tagmerge
 
 def _toolstr(ui, tool, part, default=""):
     return ui.config("merge-tools", tool + "." + part, default)
@@ -221,6 +222,16 @@
         return True, r
     return False, 0
 
+@internaltool('tagmerge', True,
+              _("automatic tag merging of %s failed! "
+                "(use 'hg resolve --tool internal:merge' or another merge "
+                "tool of your choice)\n"))
+def _itagmerge(repo, mynode, orig, fcd, fco, fca, toolconf, files, labels=None):
+    """
+    Uses the internal tag merge algorithm (experimental).
+    """
+    return tagmerge.merge(repo, fcd, fco, fca)
+
 @internaltool('dump', True)
 def _idump(repo, mynode, orig, fcd, fco, fca, toolconf, files, labels=None):
     """