linelog: correct the default value of `annotateresult.lines` This was flagged by pytype once it was tricked into using the standard `attr` package instead of the vendored copy.

phabricator: correct the default value of `phabhunk.corpus` There's only one caller to this constructor (which does provide this argument), and no direct assignments, so there's no runtime bug here. However, when pytype is tricked into using the standard `attr` package instead of the vendored version, it flags this because bytes is passed to the one constructor invocation. Tricking pytype into using the standard package will generate many more type hints, noteably around `@attr.s` decorated things.

rust-changelog: accessing the index The `Index` object is currently the one providing all DAG related algorithms, starting with simple ancestors iteration up to more advanced ones (ranges, common ancestors…). From pure Rust code, there was no way to access the changelog index for a given `Repository`, probably because `rhg` does not use any such algorithm yet.

typing: add type hints to `mercurial.policy` Mostly trivial, but this seems like the logical module to use to inject the hints from `cext`, `pure`, etc, given that this file has the fallback policy. This is a first step. There doesn't appear to be a predefined type for a module in py3.7, so those are omitted for now.

cext: correct the argument handling of `b85encode()` The type stub indicated that this argument is `Optional`, which implies None is allowed. I don't see in the documentation where that's the case for `i`[1], and trying it in `hg debugshell` resulted in the method failing with a TypeError. I guess it was typed as an `int` argument because the `p` format unit wasn't added until Python 3.3[2]. In any event, 2 clients in core (`pvec` and `obsolete`) call this with no argument supplied, and `mdiff` calls it with True. So I guess we've avoided the None arg case, and when no arg is supplied, it defaults to the 0 initialization of the `pad` variable in C. Since the `p` format unit accepts both `int` and None, as well as `bool`, I'm not bothering to bump the module version- this code is more permissive than it was, in addition to being more correct. Interestingly, when I first imported the `cext` and `pure` methods in the same manner as the previous commit, it dropped the `Optional` part of the argument type when generating `util.pyi`. No idea why. [1] https://docs.python.org/3/c-api/arg.html#numbers [2] https://docs.python.org/3/c-api/arg.html#other-objects

typing: add type hints to the `charencode` module Since this module is dynamically imported from either `mercurial.pure` or `mercurial.cext`, these hints aren't detected in `mercurial.encoding`, and need to be imported directly there during the type-checking phase. This keeps the runtime selection via the policy config in place, but allows pytype to see these as functions with proper signatures instead of just `Any`. We don't attempt to import the `mercurial.cext` version yet because there's no types stubs for that module, but this will get the ball rolling. I thought this would spill over into other modules from there, but the only two *.pyi files that changed were for `encoding` and `charencode`. Applying this to other dynamically selected modules will clean some things up in other files, so this is a start. I had originally redefined the functions in the type-checking block (like some of the `os.path` aliasing in `mercurial.util`), but this is better because we won't have another duplication of the definitions that may get out of date.