parse-tag

#!/usr/bin/env ruby

require 'pathname'
require 'optparse'

# Find scripts directory.
script = Pathname.new(__FILE__).realpath
prefix = script.dirname
script = script.basename

# Print help if no arguments are given.
ARGV[0] = "-h" if ARGV.empty?

# Default options.
options = {
	output: :relative
}

# Create CLI parser.
cli = OptionParser.new

# Set help banner.
cli.banner = <<~EOF
	About
	    Parse Git tag and print the respective add-on directory.

	Usage
	    #{script} [OPTIONS] TAG

	Options
EOF

# Define options.
cli.on("-h", "--help", "Print this manual.") do
	puts cli.help
	exit 1
end

cli.on("-a", "--absolute", "Print absolute instead of relative path (to the Git repository).") do
	options[:output] = :absolute
end

# Parse arguments.
begin
	cli.parse!
rescue OptionParser::InvalidOption
	STDERR.puts "#{script}: Invalid option. See --help."
	exit 1
end

# Release tag, e.g. Add-on/v42.
tag = ARGV.shift&.chomp

# Validate argument.
if tag&.empty?
	STDERR.puts "#{script}: Missing required argument. See --help."
	exit 1
end

# Tagged commit. e.g. 0123456789abcdef.
commit = `git rev-parse --verify --quiet "#{tag}" 2>/dev/null`.chomp

# Validate tag.
if commit.empty?
	STDERR.puts "#{script}: '#{tag}' is not a valid tag."
	exit 1
end

# Manifest file path. e.g. Add-on/Add-on.toc.
# We assume the Git tag was made by our release script, i.e. it points to a commit where the TOC file was the only file changed.
manifest = `git diff-tree --no-commit-id --name-only -r "#{commit}" 2>/dev/null | head -1`.chomp

# Validate manifest file.
if manifest.empty?
	STDERR.puts "#{script}: Couldn't find manifest file in commit with tag '#{tag}'."
	exit 1
end

# Switch output mode.
case options[:output]
when :relative
	# Print out relative path.
	puts Pathname.new(manifest).dirname
when :absolute
	# Get Git root directory.
	root = `git rev-parse --show-toplevel 2>/dev/null`.chomp

	if root.empty?
		STDERR.puts "#{script}: Failed to read repository root path."
		exit 1
	end

	# Print out absolute path.
	puts Pathname.new(root).join(manifest).realpath.dirname
else
	STDERR.puts "#{script}: Unexpected output mode '#{options[:output]}'."
	exit 1
end