convert: add docstring on convert.subversion.geturl()
The function is unusual for a bytes-handling function in Mercurial because it
can’t handle arbitrary bytes. Therefore we should document this fact.
Pointed out by Yuya Nishihara while reviewing e3b19004087a.
{
// Enforcing
"eqeqeq" : true, // true: Require triple equals (===) for comparison
"forin" : true, // true: Require filtering for..in loops with obj.hasOwnProperty()
"freeze" : true, // true: prohibits overwriting prototypes of native objects such as Array, Date etc.
"nonbsp" : true, // true: Prohibit "non-breaking whitespace" characters.
"undef" : true, // true: Require all non-global variables to be declared (prevents global leaks)
// Environments
"browser" : true // Web Browser (window, document, etc)
}