.jshintrc

typing: add type hints to most mercurial/pycompat.py functions

The `rapply` methods are left out because it's not `rapply(f, xs: _T0) -> _T0`
as I first thought- it's used somewhere to walk a collection and convert between
bytes and str.

Also, the `open()` call is partially untyped because I'm not sure what its
purpose is at this point- both the name and mode can be either bytes or str as
it is currently constituted.  It might make sense to assert that the file is
being opened in binary mode (like `namedtempfile()`) and cast the result to
`BinaryIO`, but that shouldn't be smuggled in with these other changes.  The
return is currently typed as `Any` because something suddenly got smarter and a
few uses in util.py (like readfile()) suddenly think it returns `IO[str]`
instead of `IO[bytes]` (BinaryIO), and it flags the type mismatch there.

{
    // 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)
}