typing: add type hints to pycompat.bytestr
The problem with leaving pytype to its own devices here was that for functions
that returned a bytestr, pytype inferred `Union[bytes, int]`. It now accepts
that it can be treated as plain bytes.
I wasn't able to figure out the arg type for `__getitem__`- `SupportsIndex`
(which PyCharm indicated is how the superclass function is typed) got flagged:
File "/mnt/c/Users/Matt/hg/mercurial/pycompat.py", line 236, in __getitem__:
unsupported operand type(s) for item retrieval: bytestr and SupportsIndex [unsupported-operands]
Function __getitem__ on bytestr expects int
But some caller got flagged when I marked it as `int`.
There's some minor spillover problems elsewhere- pytype doesn't seem to
recognize that `bytes.startswith()` can optionally take a 3rd and 4th arg, so
those few places have the warning disabled. It also flags where the tar API is
being abused, but that would be a tricky refactor (and would require typing
extensions until py3.7 is dropped), so disable those too.
Mercurial's documentation is kept in reStructuredText format, which is
a simple plain text format that's easy to read and edit:
http://docutils.sourceforge.net/rst.html
It's also convertible to a variety of other formats including standard
UNIX man page format and HTML. You'll need to install Docutils:
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Use the Makefile in this directory to generate the man and HTML pages.