Remove $FreeBSD$: two-line nroff pattern

Remove /^\.\\"\n\.\\"\s*\$FreeBSD\$$\n/

pkg: Add limited --debug/-d support

Add an internal debug level global:
- Level 1 (-d) currently does nothing.

- Level 2 (-d -d) enables libfetch debugging (quite verbose) so it's
possible to see what pkg is attempting to download without having
to sniff traffic.

Reviewed by: debdrup, bapt
Differential Revision: https://reviews.freebsd.org/D35756

pkg.7: Clean up mdoc

MFC after: 1 week

pkg(7): add an -r reponame option for bootstrap and add

This is limited to bootstrap/add because some real pkg(8) commands
have -r flags with an incompatible meaning/usage, e.g., pkg-audit.
pkg(7) will still commence the search as it has, but it will ignore any
repo objects without the given name so that overrides and whatnot still
work as expected.

The use of it for add is noted in the manpage; notably, that the
signature config for that repository will be used over global config if
it's specified. i.e., pkg(7) should assume that the given pkg did come
from that repository and treat it appropriately.

Reviewed by: bapt, manu
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D28524

pkg(7): rework the arguments handling

Rework the arguments handling around using getopt_long:
* add long option support
* add -4 and -6 support to enforce ipv4 or ipv6

While here fix a regression which occured between FreeBSD 12.1 and
FreeBSD 12.2 where pkg bootstrap -y stopped working

PR: 252270
MFC after: 2 weeks
Submitted by: evilham <contact@evilham.com>
Differential Revision: https://reviews.freebsd.org/D27860

fix up docs, if signature checking is enabled, the file MUST exist...

Fix multi-repository support by properly respecting 'enabled' flag.

This will read the REPOS_DIR env/config setting (default is /etc/pkg
and /usr/local/etc/pkg/repos) and use the last enabled repository.

This can be changed in the environment using a comma-separated list,
or in /usr/local/etc/pkg.conf with JSON array syntax of:
REPOS_DIR: ["/etc/pkg", "/usr/local/etc/pkg/repos"]

Approved by: bapt
MFC after: 1 week

Follow-up to r258227 and document 'enabled' as a boolean instead of
a string.

Approved by: bapt
MFC after: 2 days
X-MFC-With: r258227

Use proper capitalization for FreeBSD.org

Approved by: bapt
MFC after: 2 days

Add -f support to 'pkg bootstrap' and 'pkg add' to force installation
of pkg(8) even if already installed.

This is useful if you somehow messup pkg(8) and need to reinstall from
remote with it already being registered in the pkg(8) /var/db/pkg database.

Also add some sanity checks to 'pkg add'.

Approved by: bapt
MFC after: 2 days

A few minor mdoc improvements.

Add a pkg(7) manpage for bootstrap

Approved by: bapt
MFC after: 2 days