Homebrew/homebrew

This reverts commit 03199f2.

Closes #42935.

This needs to be `Homebrew $HOMEBREW_VERSION` so we can be adequately
filtered.

Closes #49961.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

- Use empty array when `git credential-osxkeychain` lookup fails to
  cache and avoid rerunning it when there's no valid results.
- Redirect `stderr` to avoid printing errors when there's a failure
  or no `git credential-osxkeychain` installed.

Closes #49954.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

Closes #49882.

As requested in #46578. Falls back to existing functionality.

Closes #46578.

Closes #49846.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

Closes #49841.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

Use plist_options, remove `.sh` from binary names.

Closes #49845.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

We're using /bin/bash and not /bin/sh for a reason so don't allow users
to override this (seen in #49514).

Closes #49515.

When there are merge conflicts we fail pretty hard. This is still
possible after this commit but at least we've given Git enough pointers
to make it less likely.

Closes #49299.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

Check to see if `HEAD` is the same as what we have locally. If it is:
don't bother to `git fetch`.

Closes #47888.

Closes #49219.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

Closes #47888.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

This allows there to be a user-visible description of why a bottle is
not being installed.

`bin/brew` is getting a bit bloated and it's annoying to open all of
`HOMEBREW_PREFIX` in your editor of choice and have it search through
the `Cellar`. Let's instead keep the bare minimum in `bin/brew` and
move the rest to `Library`.

Closes #49185.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>