mercurial/wireproto.py

--- a/mercurial/wireproto.py	Mon Mar 14 21:15:59 2016 -0400
+++ b/mercurial/wireproto.py	Fri Mar 11 11:37:00 2016 -0500
@@ -688,6 +688,8 @@
     caps.append('unbundle=%s' % ','.join(changegroupmod.bundlepriority))
     caps.append(
         'httpheader=%d' % repo.ui.configint('server', 'maxhttpheaderlen', 1024))
+    if repo.ui.configbool('experimental', 'httppostargs', False):
+        caps.append('httppostargs')
     return caps
 
 # If you are writing an extension and consider wrapping this function. Wrap