subrepo: use per-type config options to enable subrepos
We change subrepos.allowed from a list of allowed subrepo types to
a combination of a master switch and per-type boolean flag.
If the master switch is set, subrepos can be disabled wholesale.
If subrepos are globally enabled, then per-type options are
consulted. Mercurial repos are enabled by default. Everything else
is disabled by default.
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.