Partial implementation of
https://github.com/Homebrew/brew-evolution/pull/15, along with the ability to
search for deleted formulae in git history (inspired by #1996) which is not
described in the proposal.

See also: #1371.

Fixes https://github.com/Homebrew/homebrew-core/issues/10338

.

Closes #2287.

Signed-off-by: Alex Dunn <dunn.alex@gmail.com>

docs: grammar edits, sentence-case secondary headings

Also changes some heading levels so only one primary
heading appears per page.

audit: online - limit download time based on HTTPS determination

Fix small typos in How-to-Create-and-Maintain-a-Tap.md

Avoids unnecessary conflicts when a previously non-keg_only formula is
in the way by prioritizing keg_only before non-keg_only formulae.

This change is motivated by the upgrade of gnupg 2.0 to 2.1, since the
latter no longer depends on the gpg-agent formula, which, even if made
keg_only, still causes the link step to fail for 2.1, as gpg-agent's
non-keg version won't have been upgraded to the keg_only version at that
point (alphabetically gnupg precedes gpg-agent).

Add extend/os/linux/system_config.rb

determine_path: Fix tests FormulaUnavailableError

Report the Linux kernel, OS, and gcc versions.

Use a `Formulary`-like approach to load Casks.

Previously, the http_content_headers_and_checksum method always
downloaded the entire url, including headers. These downloads
periodically hang, outputting false positives or wreaking havoc on
the CI. Therefore, use curl's --max-time arg to prevent this by
setting a hard limit of 600 seconds when the entire file is going
to be used to detect whether the url can be changed to use the HTTPS
protocol instead of HTTP. Otherwise, if the url already is HTTPS, limit
the download time to 25 seconds since only the headers, not contents, matter.

add command 'cask outdated'

Add test for command help strings.

Remove `sort` from `each_artifact`.

secure urls + remove -k from in-doc curl command

Added highlighting of installed casks to cask search

Remove `dsl` parameter from `Cask::new`.

Update RuboCop-Cask to 0.12.0.

Querying-Brew.md: directors => directories

OPTIMIZATION_FLAGS: Use -march=native for Penryn

Default to `sudo: false` for `installer/uninstall :script`.

Use -march=native for Penryn as for other systems rather than
-march=core2 -msse4.1.

docs: add markers to ordered lists and sublists