diff -r 8604f130eb43 -r f6187e60f792 mercurial/help.py
--- a/mercurial/help.py	Fri Dec 14 13:33:12 2018 -0800
+++ b/mercurial/help.py	Fri Dec 14 13:44:46 2018 -0800
@@ -160,6 +160,8 @@
         if shortopt:
             so = '-' + shortopt
         lo = '--' + longopt
+        if isinstance(default, bool):
+            lo = '--[no-]' + longopt
 
         if isinstance(default, fancyopts.customopt):
             default = default.getdefaultvalue()