Install specific version of a Homebrew formula

brewv.sh

#!/bin/bash
#
# Install specific version of a Homebrew formula
#
# Usage: brewv.sh formula_name desired_version
#
# Notes:
# - this will unshallow your brew repo copy. It might take some time the first time 
#   you call this script
# - it will uninstall (instead of unlink) all your other versions of the formula.
#   Proper version management is out of scope of this script. Feel free to improve.
# - my "git log" uses less by default and when that happens it breaks the script 
#   Therefore we have the "--max-count=20" parameter. This might fail to find proper 
#   version if the one you wish to install is outside of this count.
#
# Author: Stanimir Karoserov ( demosten@gmail.com )
#

if [ "$#" -ne 2 ]; then
	echo "brewv.sh - installs specific version of a brew formula"
	echo "syntax: brewv.sh formula_name desired_version"
	echo "e.g.: brewv.sh swiftformat 0.39.1"
	exit 1
fi

git -C "$(brew --repo homebrew/core)" fetch --unshallow || echo "Homebrew repo already unshallowed"

commit=$(brew log --max-count=20 --oneline $1|grep $2| head -n1| cut -d ' ' -f1)
formula=$(brew log --max-count=20 --oneline $1|grep $2| head -n1| cut -d ':' -f1|cut -d ' ' -f2)

if [ -z ${commit} ] || [ -z ${formula} ]; then
	echo "No version matching '$2' for '$1'"
	exit 1
else 
	cd /usr/local/bin
	if [[ -e $formula ]]; then
		brew uninstall --force $1
	fi
	brew install https://raw.githubusercontent.com/Homebrew/homebrew-core/$commit/Formula/$formula.rb

	echo "$1 $2 installed."
fi