analytics: don't report commands run by Homebrew

upgrade: tell people that --all is a no-op.

update-test: add --to-tag option.

Fixes #788.

Apparently this is still run by people so let's tell them to save
some typing.

man: note --fail-if-changed date behaviour change.

This option is used to test updating between tags.

Store the formula used to build the keg in the keg

As requested in #1199 this updates the documentation accordingly for
that change.

man: set date when --fail-if-changed.

Set the manpage date to the existing one if we're checking for changes.
This avoids the only change being e.g. a new date.

Man exit code

update.sh: use sort instead of git tag --sort.

The --fail-if-changed option will cause `brew man`
to return a failing status code if the man files
have changed.

This is a full rewrite of the zsh completion based on the changes we
made to support external commands. A function for each brew command
handles only that command's arguments. The main completion function
dispatches the completion flow to the correct function. This
generically works with both internal and external commands.

This change includes all arguments for all internal brew commands.
Some commands are missing argument documentation due to missing help
docs.

Update `rubocop-cask` to 0.10.0.

completion: Avoid aliases with `command ls`

fix Formula path in Formula-Cookbook, support macOS

Older versions of Git don't have this flag and we don't want to block
updates for them when there's a (relatively) simple workaround.

If the user has an alias overriding the `ls` command that modifies the
output (e.g. `alias ls='ls -F'`), it will cause unexpected characters to
appear in completions. Using `command ls` forces the shell to use the
command directly, without alias expansion.

This also blackholes the stderr of `ls` when used to avoid printing
errors during completion if the requisite directory does not exist.

superenv: more 10.11 clock_gettime Autotools fixes

some build systems check ac_cv_search_clock_gettime instead of
ac_cv_func_clock_gettime so the former should also be set to "no"

libev.m4 unsets ac_cv_func_clock_gettime, but if ac_have_clock_syscall
is defined, it will leave ac_cv_func_clock_gettime alone:

  http://cvs.schmorp.de/libev/libev.m4?view=markup#l23

download_strategy: silence unzip and unrar

update.sh: hide GITHUB_HEADERS missing output.

We silenced tar in 5e3a26bf. It makes sense to make unzip and unrar
output comparably succinct.

Will only happen once but could be confusing anyway.

Rubocop style fixups

RuboCop changes.

bump-formula-pr: enhancements