support boolean git configs that are represented by the name of the setting with no value

Eg"core.bare" is the same as "core.bare = true".

Note that git treats "core.bare =" the same as "core.bare = false", so the
code had to become more complicated in order to treat the absense of a
value differently than an empty value. Ugh.

Git/GCrypt.hs

@@ -98,6 +98,7 @@ getParticiantList globalconfigrepo repo remotename = KeyIds $ parse $ firstJust
 	defaultkey = "gcrypt.participants"
 	parse (Just (ConfigValue "simple")) = []
 	parse (Just (ConfigValue b)) = words (decodeBS' b)
+	parse (Just NoConfigValue) = []
 	parse Nothing = []
 
 remoteParticipantConfigKey :: RemoteName -> ConfigKey