tap_constants: allow formulae to have @ in name.

test-bot: add missing @tap check.

Follow-up from #812 to fix handling fully-qualified versioned formulae
names.

Allows pulling https://github.com/Homebrew/homebrew-core/pull/971.

test-bot: don't run brew tests etc. when formulae.

bottle: allow --keep-old to ignore same sha256s.

If there's formulae changes or the specified argument is a formula then
don't waste time running e.g. `brew tests`.

It should refuse to change existing ones but it should allow them to be
the same and silently ignore.

bottle: fix --keep-old JSON generation.

Ensure that the JSON file contains all the bottle checksums when using
`--keep-old`. This avoids having to use the formula DSL when merging and
relies on existing integrity checks.

This change does nothing differently if `--keep-old` is not passed.

audit: detect partial component order compliance

Don't reject -L/usr/local/lib when SDKROOT is defined

Closes #844. Fixes Homebrew/homebrew-fuse#62.

brew.sh: allow cask to be run as root.

utils: fix link_path_manpages message indentation.

Otherwise looks weird with multiple items.

It also uses `sudo` for legitimate things e.g. installing `.pkg`s
systemwide.

formula: pinned keg is not eligible for cleanup

Also report Cask coverage.

docs: add missing </pre>

audit: various tweaks

If formula is pinned it shouldn't be eligible for cleanup.
Otherwise we can encounter the following behaviour:

1. Install <formula>
2. Pin <formula>
3. <formula> gets outdated
4. Install <other_formula> that depends on <formula>, which requires
up-to-date installation of <formula>. Thus, <formula> gets updated.
5. Now, if we cleanup <formula> we don't remove pin, so it points to
the keg which doesn't exist any longer. The right behaviour is not
to cleanup pinned kegs, which is done in this commit.

Also see #831 for further info.

formula_installer: install deps of dep before dep

Dependencies/requirements of a dependency need to be installed/satisfied
before the dependency. The fact that @pour_failed may be false is
irrelevant to that imperative if we weren't pouring to begin with, so
this commit now checks for that case as well.

scm/git: make --homebrew=print-path use realpath.

update.sh: reset pre-stash, die if stash fails.

/usr/local/lib is removed from the default linker search path when
SDKROOT is defined or sysroot is specified.

Homebrew sometimes sets SDKROOT without setting a sysroot as of 45e138ff.

docs: fix a typo in plist_options?

While using `"true"` instead of `true` wouldn't break anything, it doesn't
seem to be expected, and using `"false"` instead of `false` _would_ break
things.

Allow deprecated hash syntax in Cask headers

bottles: translate foo@1.2 to fooAT1.2

Add `--full-name` option to `brew deps`

This allows changed formulae in taps to be tested in the proper order.
See #738 for more details.