tests/revnamesext.py

typing: declare the `_phasesets` member of `phasecache` to be `Optional`

Something in this area got flagged while making the repository class visible to
pytype (instead of being typed as `Any`).  A None assignment to something not
optional is wrong, and when I tried setting it to `{}` to keep it non-Optional,
some tests failed.  There are checks for the attr being None elsewhere, so this
seems to have just been an oversight.

# Dummy extension to define a namespace containing revision names


from mercurial import namespaces


def reposetup(ui, repo):
    names = {b'r%d' % rev: repo[rev].node() for rev in repo}
    namemap = lambda r, name: names.get(name)
    nodemap = lambda r, node: [b'r%d' % repo[node].rev()]

    ns = namespaces.namespace(
        b'revnames',
        templatename=b'revname',
        logname=b'revname',
        listnames=lambda r: names.keys(),
        namemap=namemap,
        nodemap=nodemap,
    )
    repo.names.addnamespace(ns)