diff -r 430fdb717549 -r c6a61298ac32 mercurial/patch.py
--- a/mercurial/patch.py	Sat Mar 03 12:39:14 2018 -0800
+++ b/mercurial/patch.py	Sat Mar 03 12:39:14 2018 -0800
@@ -2256,6 +2256,7 @@
         'context': get('unified', getter=ui.config),
     }
     buildopts['worddiff'] = ui.configbool('experimental', 'worddiff')
+    buildopts['xdiff'] = ui.configbool('experimental', 'xdiff')
 
     if git:
         buildopts['git'] = get('git')