manifest: remove check for non-contexts in _dirmancache
It looks like the _dirmancache has contained only manifest contexts
since
d79c141fdf41 (manifest: remove usages of manifest.read,
2016-11-10).
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.