mercurial/__init__.py

typing: lock in new pytype gains from making revlog related classes typeable

These were pretty clean changes in the pyi files from earlier in this series, so
add them to the code to make it more understandable.

There's one more trivial hint that can be added to the return of
`mercurial.revlogutils.rewrite._filelog_from_filename()`, however it needs to be
imported from '..' under the conditional of `typing.TYPE_CHECKING`, and that
seems to confuse the import checker- possibly because there's already an import
block from that level.  (I would have expected a message about multiple import
statements in this case, but got one about higher level imports should come
first, no matter where I put the import statement.)

# __init__.py - Startup and module loading logic for Mercurial.
#
# Copyright 2015 Gregory Szorc <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.


# Allow 'from mercurial import demandimport' to keep working.
import hgdemandimport

demandimport = hgdemandimport