configitems: register the 'server.zliblevel' config

mercurial/configitems.py

@@ -140,6 +140,9 b" coreconfigitem('server', 'uncompressedal"
 coreconfigitem('server', 'validate',
     default=False,
 )
+coreconfigitem('server', 'zliblevel',
+    default=-1,
+)
 coreconfigitem('ui', 'clonebundleprefers',
     default=list,
 )

mercurial/hgweb/protocol.py

@@ -135,7 +135,7 b' class webproto(wireproto.abstractserverp'
         # Don't allow untrusted settings because disabling compression or
         # setting a very high compression level could lead to flooding
         # the server's network or CPU.
-        opts = {'level': self.ui.configint('server', 'zliblevel', -1)}
+        opts = {'level': self.ui.configint('server', 'zliblevel')}
         return HGTYPE, util.compengines['zlib'], opts
 
 def iscmd(cmd):