Add official external commands to manpage.

*/diagnostic: tweak messaging.

list: fix exit code for --verbose and --pinned

These are the ones that are auto-installed without tapping and it makes
sense to make them more prominent in our documentation as we've
offloaded various functionality over the years to each of them.

Update some messaging based on recent user confusion and the
`/usr/local/Homebrew` and Ruby 2 migrations.

update-test: fix tag updating, skip core tap.

Fix updating the `stable` branch used for tagged updates and ensure
that the core tap isn’t retapped (the slowest part by far of this test).

`brew list --verbose <formulae>` lists only those kegs that
are installed and exits with 0 if all <formulae> installed.
If one or more formulae from <formulae> are not installed, the
command lists only installed versions and exits with 1.

`brew --pinned formula` exits with 1 if formula is not pinned.

Fixes #1172

help: support `#:` help in external commands.

install: remove not updated warning.

Fix `Tty.gray`.

Refactor Tty.

Use separate RuboCop configs for formulae and core code.

This is no longer relevant after moving to taps/tags and if ever
re-added it should probably target homebrew/core.

Fixes #1194.

Fixes https://github.com/Homebrew/homebrew-test-bot/issues/3

analytics: don't report commands run by Homebrew

upgrade: tell people that --all is a no-op.

update-test: add --to-tag option.

Fixes #788.

Apparently this is still run by people so let's tell them to save
some typing.

man: note --fail-if-changed date behaviour change.

This option is used to test updating between tags.