downgrade-homebrew-formula.md

Homebrew is pretty frustrating for downgrading, here are the steps (last known version to work with fishis v2.10)

Steps for people in the future that need to do this:

# remove current version
brew uninstall navi

# find formula/bottle
# launches url
brew info --github navi

# from github url
# 1. locate version 
# 2. click 'History'
# 3. locate for the version from @BrewTestBot
# 4. click 'Commit' > 'View File' > Raw
# 5. fetch using `cURL`
curl -O https://raw.githubusercontent.com/Homebrew/homebrew-core/7c7f18795fac61747fe383d7c22ec183d5283362/Formula/navi.rb

# install older version
brew install navi.rb && rm navi.rb

# optional, pin until fix is known
brew pin navi