Add labeled fences to most code blocks, monospace terms where
appropriate, omit "$" when referring to variables

Also works around bug in Jekyll where a URL with a "#" will cause links
in the same paragraph to not have their extensions replaced by using
"#" instead.

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

Fixes to spelling and punctuation for consistency and readability.

The "Messaging" heading was failing to be rendered due to a missing newline between it and "Convenience Tools".

resolves https://github.com/Homebrew/brew/issues/1821

There are some formulas in which Homebrew symlinks configuration files
into /usr/local/etc/ instead of copying them, resulting in custom
settings being overwritten on package upgrades. This addition to the
documentation illustrates one way to avoid this behavior by ensuring the
configure script is told where to copy the configuration file(s).

Refs https://github.com/Homebrew/homebrew-core/issues/8711

Mostly related to the newer ways we’re handling versions and the
incoming deprecation of devel-only, head-only and versions.

Addressing a few spots where I looked for terminology and did not find what I was looking for. Input based on a recent [podcast with Mike](https://changelog.com/podcast/223)

Closes #1040.

Not quite a mass replacement as I've used OS X and Mac OS X where
describing specific older versions and added compatibility methods
for things in the DSL.

This document lists Tigerbrew and Linuxbrew as interesting forks, not
branches (they used to be "Interesting Branches (aka forks)" but that
changed in b7455469), so "Interesting Taps & Branches" is a more fitting
title.

The term "branches" is also presumably confusing to folks with a shallow
understanding of GitHub and/or git who may not realize how GitHub forks
and git branches are related.

`--HEAD` defaults to `:branch => "master"` so document that.

Closes #722.

Make multiple replacements if using the block form.

Closes #71.

Signed-off-by: Andrew Janke <andrew@apjanke.net>

Closes Homebrew/homebrew#50632.

Signed-off-by: Xu Cheng <xucheng@me.com>

Closes Homebrew/homebrew#50146.

Signed-off-by: Alex Dunn <adunn@ucsb.edu>

See https://github.com/Homebrew/homebrew/pull/50130#discussion_r56254860

If a formula's class name contains an uppercase-spelled acronym, the
messages given by `brew install` can be pretty confusing (it recommends
a formula named exactly the same…)

Closes Homebrew/homebrew#49639.

Signed-off-by: Tim D. Smith <git@tim-smith.us>

Based on recent feedback on some pull requests, I touched up the section about adding tests to formula.
I wanted to make it clearer that the examples demonstrate how to create files on the fly and add a pointer to the tinyxml2 formula (DomT4 pointed it out to me as a good example).

Closes Homebrew/homebrew#49641.

Signed-off-by: Dominyk Tiller <dominyktiller@gmail.com>