Today the Homebrew maintainers elected a new PLC, TSC and project lead.
Documentation is to follow detailing exactly the responsibilities for
each of these roles but adjust these to reflect the current state until
that point.

- Move `odeprecated` to `odisabled`
- Remove `odisabled`
- Enable automatic cleanup on install/reinstall/upgrade.

This change fixes a syntax error introduced in b278165d

If set, Homebrew will fail if on the failure of installation from a
bottle rather than falling back to building from source.

- Add some `odeprecated`
- Make some `odeprecated` now `odisabled`
- Remove `odisabled` code.
- Remove old update migrations
- Remove GCC 4.0 compiler
- Remove Tiger-only code
- Remove 32-bit-only code
- Remove use of LD64
- Remove GCC 4.3 - 4.8 support.

This will become the default in a later version of Homebrew but has an
opt-out through HOMEBREW_NO_INSTALL_CLEANUP.

Also, always cleanup files older than 120 days and set the general
default value for "old" logs, casks etc. to 30 days.

more.

     `brew`'s `man` page's 'ENVIRONMENT' section is intended to list only those
environment variables that users can set, not any that Homebrew sets as part of
its operation.

Note that the `HOMEBREW_FORCE_BREWED_` vars are automatically set if the system `git` and `curl` are too old. Drop mention of `HOMEBREW_GIT` which isn't user-settable.

Replace <var> tags with markup for italicized monospaced text in Markdown.
This requires the source to not combine bracketed and backticked text.

Work around ronn's inability to nest indents within list items by modifying its output to add a line break and indent after lines ending with a colon that aren't a list item's first line. This allows `brew.1.md.erb` to join the commands' help text without extra line breaks, which avoids the issue where kramdown was turning any command specs containing pipe characters into tables in the HTML output.

And remove the Homebrew/homebrew-core lead maintainer role.

Also add some who were missing (sorry folks) and our Linux maintainers.

Let's document these so people know who the leadership team behind the
project is.

Rather than relying on a `HOMEBREW_FORCE_BOTTLE` variable (which ends
up doing silly things like forcing bottle usage even when options are
provided) instead handle this at the `or_later` bottle detection
level so on prerelease versions of macOS any bottle looks like an
`or_later` bottle (unless various environment variables are set).

Fixes issues noted in:
https://github.com/Homebrew/brew/pull/4520#issuecomment-407229605

This does the equivalent of always passing `--force-bottle`. This will
be enabled by default on Mojave to allow people to avoid building
everything from source until our porting and bottling is a bit further
along.

* update references in `--cc` flag, using modern gcc examples
* note that issues should not be filed if `--cc` flag is used
* remove reference to `HOMEBREW_CC` as it should not be exposed to users
* generate manpages using `brew man` with these changes

Properly update man pages using the local brew executable (from the repo),
and copy the man pages to the repo.

Because of this messing with the user's path:
https://github.com/Homebrew/brew/blob/
    efc02899/bin/brew#L68
brew uses /usr/bin/git over brewed git, even when the former is
problematically old.
There may also be other reasons a user prefers to use brewed git.

There was already a HOMEBREW_FORCE_BREWED_CURL option and a
HOMEBREW_SYSTEM_CURL_TOO_OLD check to set it. This mostly copies those
to implement HOMEBREW_FORCE_BREWED_GIT & HOMEBREW_SYSTEM_GIT_TOO_OLD.

See also: https://github.com/Linuxbrew/brew/issues/736

This reverts commit 4475651b.

Address the confusion in #4015.

Extract `brew bundle` and `brew services` docs from their help. Add a
little for `brew cask` until we can think about e.g. merging the
manpages.

Allow users to specify they want `brew upgrade --cleanup` to always be
run when they run `brew upgrade`.

Make `brew irb` optionally support `pry`. While doing so, also make it a `dev-cmd`.

These are nicer on the eyes.

bin/brew will recognize NO_COLOR variable and copy it to
HOMEBREW_NO_COLOR

Make this generic; it doesn't matter what version this is and this will
future proof it.