Demo using a hook to restrict branch names

git_branch.sh

#!/bin/bash
# Demo using a hook to restrict branch names
# !Run in a temp dir!

set -ue

main () {
echo \> Setup
    mkdir work
    cd work
    git init
    echo "Initial state" > file
    git add file
    git commit -m "Initial commit"
    cd -

    git clone --bare work server
    cd server
echo \> Write ref update hook
    cat <<-EOF > hooks/update
	#!/bin/bash
	ref_name=\$1
	old_ref=\$2
	new_ref=\$3
	echo "Update \${ref_name}: \$old_ref → \$new_ref"

	if [ "\$old_ref" != "0000000000000000000000000000000000000000" ]; then
	    echo "Existing branches may be updated"
	    exit 0
	fi

	if [[ "\$ref_name" =~ "refs/heads/" ]]; then
	    # Check branch name matches policy
	    if [[ "\${ref_name}" =~ "/jira" ]]; then
	        echo "Branch OK"
	        exit 0
	    else
	        echo "Policy: Branch must start with \"jira\""
	        exit 1
	    fi
	else
	    echo "Not a branch: \$ref_name"
	fi
	EOF
    chmod +x hooks/update
    cd -

    cd work
    git remote add server ../server
    cd -
echo
echo \> Make a change
    cd work
    echo "Modified state" > file
    git commit -m "Modification" file
    git push server master
    cd -
echo
echo \> Submit a tag
    cd work
    git tag testtag
    git push server testtag
    cd -
echo
echo \> Make good and bad branches
    cd work
    git checkout -b jira42
    git checkout -b nope24
    git push server nope24 jira42 || true
    cd -
}

if [ "${1:-}" = "clean" ]; then
    rm -rf work server
else
    main
fi