- Add `HOMEBREW_NO_BOOTSNAP` as well as `HOMEBREW_BOOTSNAP`
- Guard the whole file rather than `raise` on inclusion.
- Use `HOMEBREW_CACHE` instead of `HOMEBREW_TEMP`
- Don't try to use Bootsnap with macOS portable ruby
- rename to `homebrew_bootsnap.rb` to avoid conflicting with the
`bootsnap.rb` we need to `require`
- if the `require` fails: run bundler (until we vendor this gem)
> Bootsnap is a library that plugs into Ruby, with optional support
> for ActiveSupport and YAML, to optimize and cache expensive
> computations.
https://github.com/Shopify/bootsnap
For our case that translates to "repeated calls to `brew` have
reductions in the time spend `require`ing speeding up the process
boot time".
For example:
```
$ hyperfine --warmup=2 "unset HOMEBREW_BOOTSNAP; brew info wget" "export HOMEBREW_BOOTSNAP=1; brew info wget"
Benchmark #1: unset HOMEBREW_BOOTSNAP; brew info wget
Time (mean ± σ): 2.417 s ± 0.032 s [User: 659.0 ms, System: 855.5 ms]
Range (min … max): 2.382 s … 2.464 s 10 runs
Benchmark #2: export HOMEBREW_BOOTSNAP=1; brew info wget
Time (mean ± σ): 1.862 s ± 0.064 s [User: 425.3 ms, System: 566.8 ms]
Range (min … max): 1.736 s … 1.952 s 10 runs
Summary
'export HOMEBREW_BOOTSNAP=1; brew info wget' ran
1.30 ± 0.05 times faster than 'unset HOMEBREW_BOOTSNAP; brew info wget'
```
Rather than having to manually keep track of what version each thing in
here is and copy files around by hand on update let's use Bundler's
standalone mode and careful use of `.gitignore` to help us do it.
This means a `bundle update --standalone` will allow us to update all
gems in vendor.
We could consider vendoring other gems this way in future but I'd
suggest only doing this for gems with no dependencies or at least gems
with no native extensions. The only gem this applies to that we
currently use is `ruby-prof` and I'm not convinced it's widely used
enough to warrant vendoring for everyone. Perhaps that's another
criteria: it should be functionality that's used by non-developer
commands and/or normal Homebrew usage.
