typing: add some type annotations to mercurial/phases.py
Some of these were helpful in typing other modules, and then I typed the
easy-ish ones. Black forces the long `Phasedefaults` definition to be wrapped,
which pytype seems OK with (as shown with `reveal_type()`), but it does seem to
confuse PyCharm a bit.
Differential Revision: https://phab.mercurial-scm.org/D10126
Mercurial
=========
Mercurial is a fast, easy to use, distributed revision control tool
for software developers.
Basic install::
$ make # see install targets
$ make install # do a system-wide install
$ hg debuginstall # sanity-check setup
$ hg # see help
Running without installing::
$ make local # build for inplace usage
$ ./hg --version # should show the latest version
See https://mercurial-scm.org/ for detailed installation
instructions, platform-specific notes, and Mercurial user information.