Fix `Pkg#uninstall` not calling `MacOS.undeletable?` for all files.

formula: Remove reference to homebrew/x11

Fix parsing extension from URL.

That tap is now defunct.

Signed-off-by: Bob W. Hogg <rwhogg@linux.com>

Delete `:focus`.

travis.yml: only build the master branch.

audit: Port patches audit code to a rubocop and add tests

This avoid two weird things:

- scary messages when building tags fails
- two builds being run instead of one when people create a PR and a
  branch on the Homebrew/brew repo (rather than their fork).

Detect `Tap` in `CaskLoader`.

audit: add additional php header ignore patterns

Tap.each: return an enumerable when no block given

Remove `brew cask _checkurl`.

formula_cellar_checks: check_non_libraries only for new formulae

This check is overly opinionated and leads to audit failures no one
cares to fix, so let's only run it for new formulae.

formula_desc_cop: add 'x86' to VALID_LOWERCASE_WORDS

Put the five executables in a list

audit: Port audit_urls strict rules to rubocop, add tests, autocorrect

audit: fix bug where `brew audit foo` runs every style check.

audit: Port dependency rules from line_problems to rubocop and add tests

docs/brew-tap.md: Reference dunn's Emacs tap

formula: Remove reference to Homebrew/Homebrew

edavis' repo currently points to homebrew/emacs,
which has since been moved to dunn/emacs.

Signed-off-by: Bob W. Hogg <rwhogg@linux.com>

That repo is now defunct. Reference homebrew-core instead.

Signed-off-by: Bob W. Hogg <rwhogg@linux.com>

Simplify `assert_only_one_stanza_allowed`.

This also helpfully avoids always building all dependencies from source
when passing `--build-bottle` or forcing all bottles when passing
`--force-bottle`.

Tweak preserve link status on reinstall/upgrade.

Treat a `brew install` command as normal i.e. link by default unless
keg-only and only specify whether a keg should be linked when upgrading
or reinstalling. Also, adjust the naming accordingly so it's more
obvious that this is the case.