Merge pull request Homebrew#4457 from commitay/latest-autoupdate

cask audit: check for `latest` with `auto_updates`

Merge pull request Homebrew#4467 from MikeMcQuaid/portable-ruby-clean…

…up-gems

ruby.sh: cleanup gems on portable Ruby installation.

Merge pull request Homebrew#4453 from reitermarkus/fix-system-command

Fix `SystemCommand` `:path`.

Merge pull request Homebrew#4450 from MikeMcQuaid/no-really-no-beta-s…

…upport

diagnostic: be clearer about what we support.

Merge pull request Homebrew#4406 from commitay/python-3.7

language/python, docs: updates for python 3.7

Merge pull request Homebrew#4444 from ilovezfs/link-fix-undefined

link: fix undefined `dep_f`

Merge pull request Homebrew#4426 from reitermarkus/refactor-system-co…

…mmand-plist

Simplify `Hbc::SystemCommand::Result#plist`.

Merge pull request Homebrew#4320 from lucafavatella/brew-cask-doctor

Fix `brew cask doctor` for non-standard installation location

Merge pull request Homebrew#4327 from reitermarkus/dependency-order-cop

Support constants in `DependencyOrder` cop.

Merge pull request Homebrew#4275 from DomT4/Mojave_DevTools_Updates

10.14: recognise Xcode 10.0 & add pkg-config files.