twig-checkout-parent

#!/usr/bin/env ruby

require 'rubygems'
require 'twig'

def help_content
  <<-HELP

twig-checkout-parent
====================

Checks out a branch's parent branch.

Synopsis
--------

  twig checkout-parent [-b|--branch <branch>]

Description
-----------

  Checks out the current branch's parent branch, if any, based on the current
  branch's `diff-branch` property.

  You can use this with `twig checkout-child` to traverse your tree of branches.

Options
-------

  `-b` or `--branch`: Checks out the parent branch of the given branch, rather
  than the current branch.

See also
--------

  twig-checkout-child
  twig-create-branch

Subcommand for Twig: <http://rondevera.github.io/twig/>
Author: Ron DeVera <http://rondevera.com>

HELP
end

args = ARGV.dup

if args.include?('--help')
  puts help_content
  exit
end

twig = Twig.new(:read_options => true)
target_branch = twig.target_branch
parent_branch_name = target_branch.parent_name

if parent_branch_name && !parent_branch_name.empty?
  exec %{git checkout "#{parent_branch_name}"}
else
  parent_property = Twig::Branch::PARENT_PROPERTY
  abort %{The branch "#{target_branch}" has no known parent branch.\n} \
    "To set the parent branch, run:\n\n" \
    "  twig diff-branch <parent branch name> -b #{target_branch}"
end