Reuse more code to avoid errors due to duplication.

cask doctor: add homebrew_cask_opts

system_config: don't output HOMEBREW_RUBY_WARNINGS

Upgraded use of AWS Ruby SDK for S3

It's set by default and the output is pretty obvious if changed.

When S3DownloadStrategy is detected in DownloadStrategyDetector an attempt
is made to install & require the aws-sdk-s3 gem.

The AWS S3 SDK is used to sign the URL and handed off to curl_download.

Added Homebrew.install_gem!

Useful when gem does not install with executable

fix clang build version on Ubuntu Artful

Ported from https://github.com/Linuxbrew/brew/pull/621

tab: cleanup various methods.

Formula#to_hash: cleanup method.

Revert "build: do not skip runtime deps of buildtime deps"

Use some newer Ruby syntax and improve readability.

Use some newer Ruby functionality and avoid calling `deps` multiple
times when not necessary.

Additionally, remove the unneeded `rubocop:disable`.

Improve detection of file extensions in CurlDownloadStrategy

cli : Add basic arg parser and use it for parsing `brew audit` args

fix: crash when curl is not installed

Fix `MethodDeprecatedError` output.

java_requirement, cask dsl caveats: java 10

Fix broken support GPG containers with embedded signatures

Audit use of :run dependencies.

These are a no-op so let's remove them.

/usr/bin/which -> type -P

url "https://get.filebot.net/filebot/latest/FileBot_#{version}-darwin.tar.xz.gpg"
gpg :embedded, key_url: 'https://raw.githubusercontent.com/filebot/plugins/master/gpg/maintainer.pub'

Migrated from https://github.com/Linuxbrew/brew/pull/621

keg: delete __pycache__ directory.

/bin/cat -> cat

this allows odd linux installations (Android) to function

upgrade: make pinned error have correct exit code.

Don't use Linuxbrew/homebrew-core (yet, at least).

Also, display before saying "no packages to upgrade".

Fixes #3936.

This can't be tapped on vanilla Homebrew/brew because things like e.g.
`GlibcRequirement` are missing. We will put this back when the Linuxbrew
to Homebrew migration is complete.

install: add --include-test option.