* Replaced ; with && under Update Bug in README.md.

* Updated issue template's brew update fix.

Brew-Test-Bot-For-Core-Contributors: fix broken link

Fix missing `magenta` in Tty.

Remove `exist?` check for `brew-cask-tests.rb`.

cask tty removed

Restrict TMPDIR etc. changes to install, post_install and test

See discussion in Homebrew/brew#800.

various: update CI links.

brew.sh: complain when running Homebrew as root.

As discussed: announce that we are deprecating running Homebrew as the
root user as it's insecure and requires disabling the sandbox.

Fixes #796.

diagnostic: tweak /usr/local messaging.

Highlight that the main reason for preferring /usr/local is because of
bottles. There's been some confusion around this e.g.
https://github.com/Homebrew/homebrew-core/issues/3968

config: set TMPDIR, TEMP and TMP to HOMEBREW_TEMP

Improve HOMEBREW_BREW_FILE unset failure case.

Unify heredoc style.

Allow per-cask `cleanup`.

Print a better exception message and handle this in more cases rather
than producing confusing errors when it’s unset.

bin/brew: improve $HOMEBREW_REPOSITORY/bin/brew handling.

brew.sh: don't require /usr/local/Cellar creation.

update-report: also link `brew*.1` manpages.

Merge Cask’s `Pathname` extension with Homebrew’s.

Add vendored `plist` to ReadMe.

Otherwise if your `HOMEBREW_PREFIX` and `HOMEBREW_REPOSITORY` are not
equal then your tap manpages will be linked but your `brew*` ones will
not.

If `/usr/local` is the prefix but not the repository (so bottles can be
used) then running `/usr/local/bin/brew` works great but
`$HOMEBREW_REPOSITORY/bin/brew` assumes the prefix is
`$HOMEBREW_REPOSITORY`. This is a pain when doing work on the Homebrew
repository and having e.g. `bin` in your `$PATH`. Improve this
behaviour so `bin/brew` knows how to handle this situation.

This will enable this code to be reused in a future commit and makes it
more obvious what’s being done.

The previous approach of trying to do it on one line was confusing.