version

#! /bin/sh
# NAME
#        version — Write the current version number of this “git” repository
#
# SYNOPSIS
#        version
#
# DESCRIPTION
#        Looks for the last “version-*” tag in order to build a version number
#        compliant with Semantic Versioning 2.0.0. Unreleased version are marked
#        with “-snapshot” and a build number (the shortened SHA1 hash). When
#        there are uncommited changes, inserts “-snapshot.dirty” in the
#        outputted version number.
#
# ENVIRONMENT VARIABLES
#        VERSION_INCREMENT
#               Specifies the part to increment when the current version is not
#               a release (a tagged version). Valid values: “1.0.0”, “0.1.0”,
#               “0.0.1”.
#               (default: “0.1.0”)
#
# AUTHOR
#        jcbrinfo <jcbrinfo@users.noreply.github.com>
#
# LICENSING
#        Copyright (c) 2016, jcbrinfo <jcbrinfo@users.noreply.github.com>.
#
#        Permission to use, copy, modify, and/or distribute this software for
#        any purpose with or without fee is hereby granted, provided that the
#        above copyright notice and this permission notice appear in all copies.
#
#        THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANT-
#        IES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
#        MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
#        ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
#        WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
#        ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
#        OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

PREFIX=version-
version=
major=
minor=
patch_tags=
patch=
is_release=0
tags=
hash=

## increment_version version
# Increments the specified version number.
#
# @param version the version number, in the `X.Y.Z` format
increment_version() {
	major="${1%%.*}"
	minor="${1#*.}"
	minor="${minor%.*}"
	patch_tags="${1##*.}"
	patch="${patch_tags%%-*}"
	tags="${patch_tags#-*}"

	case "${VERSION_INCREMENT}" in
	1.0.0)
		major=$((major + 1))
		minor=0
		patch=0
		;;
	0.0.1)
		patch=$((patch + 1))
		;;
	*)
		minor=$((minor + 1))
		patch=0
		;;
	esac
	if [ "$patch" = "$patch_tags" ]; then
		printf '%s.%s.%s' "${major}" "${minor}" "${patch}"
	else
		printf '%s.%s.%s-%s' "${major}" "${minor}" "${patch}" "${tags}"
	fi
}

## get_hash
# Writes the hash of HEAD.
get_hash() {
	git rev-parse --verify --quiet --short HEAD || printf '????'
}

## append_tags version tags
# Appends pre-release tags to the sepcified version.
#
# @param version the version number, in the `X.Y.Z` or `X.Y.Z-foo` format
# @param tags a dot-separated list of tags
append_tags() {
	case "${version}" in
	*-*)
		printf '%s.%s' "$1" "$2"
		;;
	*)
		printf '%s-%s' "$1" "$2"
		;;
	esac
}

# ##############################################################################
# Main routine

{
	version=$(git describe --tags --exact-match --match "${PREFIX}"'*' \
			2> /dev/null)
} && {
	is_release=1
	version="${version#"${PREFIX}"}"
	true
} || {
	{
		version=$(git describe --tags --abbrev=0 --match "${PREFIX}"'*' \
				2> /dev/null)
	} && {
		version="${version#"${PREFIX}"}"
		true
	} || {
		version=0.0.0
	}
}

if [ -n "$(git status --porcelain)" ]; then
	# The working directory has uncommited changes.
	version=$(increment_version "${version}")
	hash=$(get_hash)
	append_tags "${version}" 'snapshot.dirty'
	printf '+%s\n' "${hash}"
elif [ "${is_release}" = 0 ]; then
	version=$(increment_version "${version}")
	hash=$(get_hash)
	append_tags "${version}" 'snapshot'
	printf '+%s\n' "${hash}"
else
	printf '%s\n' "${version}"
fi