* Fix brew completion for `brew install`
* Using `brew search` rather than `brew --repository`
- Homebrew migrated the directory holding their Formulas into Taps, breaking fish's completions.
- New method to find all Homebrew-core Formulas
- Compatible with old versions of Homebrew and more future proof
* Replace fixed path to search formula with `brew --repository`
* Replace `sed` with builtin `string replace`
This is already done by fish before calling the completion.
It breaks completion with combiners (#2025) and also with wrappers.
(This does not include git because that's better solved in #2145)
Using arg completion
Context-based completion for most of commands (i.e. only installed
packages for upgrade or remove, only outdated for upgrade and so on)
