githooks/pre-commit.shellcheck

#!/bin/bash

set -e

function check_dependencies_installed() {
	for dependency in xargs shellcheck; do
		if ! command -v "$dependency" &>/dev/null; then
			printf '\e[1;31m[error]\e[0m \e[1mdependency\[0m is not installed.\n'
			exit 1
		fi
	done
}

function get_staged_files {
	if ! git rev-parse --verify HEAD &> /dev/null; then
		printf '\e[1;31m[error]\e[0m \e[1mHEAD\e[0m does not point to a commit.\n'
		exit 1
	fi

	git diff-index --cached --name-only HEAD
}

function get_shell_files {
	get_staged_files | xargs 'file' | grep 'shell script' | cut -d ':' -f 1
	get_staged_files | grep --regexp=".*\.sh$" --regexp="\.bash.*$" --regexp="\.zsh.*$"
}

function main {
	check_dependencies_installed

	declare -a files=()
	while read -r file; do
		files[${files[@]}+1]="$file"
	done < <(get_shell_files)

	if [[ "${#files[@]}" -ne 0 ]]; then
		shellcheck "${files[@]}"
	fi
}

main