git-post-checkout-master-main-hook

#!/bin/bash
# Exits with status 1 when checking out the master branch and a "main" branch
# is available

prev_head=$1
new_head=$2
branch_checkout=$3

# Ignore any non-branch checkouts
if [[ "$branch_checkout" -ne 1 ]]; then
	exit 0
fi

# if we don't have a main branch, exit early
if ! git describe main > /dev/null; then
	exit 0
fi

remotes="origin gitlab github"
master_branch="master"
for remote in $remotes; do
	git remote | grep --quiet "$remote"
	if [[ $? -eq 0 ]]; then
		master_branch="$remote/$master_branch"
		break
	fi
done


master_commit=$(git rev-list -1 $master_branch)

if [[ "$new_head" == "$master_commit" ]]; then
	echo "WARNING: the master branch is no longer in use"
	exit 1
fi