git-version

#!/usr/bin/env bash

# SPDX-FileCopyrightText: 2021 Robin Vobruba <hoijui.quaero@gmail.com>
#
# SPDX-License-Identifier: GPL-3.0-or-later
#
# See the output of "$0 -h" for details.

# Exit immediately on each error and unset variable;
# see: https://vaneyckt.io/posts/safer_bash_scripts_with_set_euxo_pipefail/
#set -Eeuo pipefail
set -Eeu

script_dir=$(dirname "$(readlink -f "${BASH_SOURCE[0]}")")

APP_NAME="Git Version printer"
empty_on_error=false

print_help() {

	script_name="$(basename "$0")"
	echo "$APP_NAME - Compiles a git based version string for the project."
	echo "It is based on 'git describe'"
	echo
	echo "Usage:"
	echo "  $script_name [OPTIONS] [repo-dir]"
	echo "Options:"
	echo "  -h, --help              Print this usage help and exit"
	echo "  -e, --empty-on-error    Return an empty string, instead of an error, when the supplied dir is not a valid git repo"
	echo "Examples:"
	echo "  $script_name"
	echo "  $script_name rel/path/to/repo"
	echo "  $script_name --help"
	echo "  $script_name -e"
}

# read command-line args
POSITIONAL=()
while [[ $# -gt 0 ]]
do
	arg="$1"
	shift # $2 -> $1, $3 -> $2, ...

	case "$arg" in
		-h|--help)
			print_help
			exit 0
			;;
		-e|--empty-on-error)
			empty_on_error=true
			;;
		*) # non-/unknown option
			POSITIONAL+=("${arg}") # save it in an array for later
			;;
	esac
done
set -- "${POSITIONAL[@]}" # restore positional parameters

repo_dir="${1:-.}"

if [ ! -e "$repo_dir/.git" ]
then
	if $empty_on_error
	then
		exit 0
	fi
	>&2 echo "ERROR: Not a valid git repo: '$repo_dir'"
	print_help
	exit 1
fi

repo_dir_abs="$(cd "$repo_dir"; pwd)"

git \
	-C "$repo_dir_abs" \
	describe \
	--long \
	--dirty \
	--candidates=99 \
	--always \
	--first-parent 2> /dev/null