Simple script to help web designers work with and release compiled assets in the same git branch as the source assets.

compile_and_commit_assets.rb

#!/usr/bin/env ruby

#----------------------------------------------------------------------------
# INFO:
#
# Simple script for web designers working on git repositories where source
# assets and compiled assets have to be stored in the same branch.
#
# The goal: generating assets safely and into a separate commit.
#
# This script helps prevent workflow errors (compiled assets in a separate
# commit, and lots of checking to avoid mistakes).
#
# USAGE:
#
# 1. Copy this script into your project, modify the MyConfig methods
# 2. Add and commit this file.
# 3. Run it on a clean repository.
#
# SUPPORT:
#
# None promised, but feel free to ask.
#
# If tool is useful enough, I'll turn it into an official project/gem and
# release, etc.
#
# TODO
#   - check to make sure compiled assets were NOT committed accidentally (only "generated commits" should include them)
#   - turn this into a proper gem.
#

#----------------------------------------------------------------------------
# Copyright 2016 Cezary Baginski <cezary@chronomantic.net>
#
# Licensed under the Apache License, Version 2.0 (the "License"); you may not
# use this file except in compliance with the License.
#
#  You may obtain a copy of the License at
#
#  http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.  See the
# License for the specific language governing permissions and limitations under
# the License.
#----------------------------------------------------------------------------


require 'English'
require 'fileutils'

class MyConfig
  def commit_message
    "regenerated assets"
  end

  def compiled_asset_dir
    "dist"
  end

  def compile_assets_command_args
    %w(sass -C foo.scss dist/foo.css)
  end
end

class AssetCommit
  attr_reader :config
  def initialize(config)
    @config = config
  end

  def commit
    reset_asset_dir
    check_modified_files
    check_untracked_files

    clean_asset_dir
    generate_asset_files
    add_asset_files
    check_unmodified_assets
    commit_assets
  end

  private

  def run(*args)
    abort "Error: Command failed: #{args.join(" ").inspect}" unless system(*args)
  end

  def reset_asset_dir
    puts "Checking out existing assets"
    FileUtils.rm_rf(config.compiled_asset_dir)
    args = %W(git checkout HEAD #{config.compiled_asset_dir})
    run(*args)
  end

  def clean_asset_dir
    puts "Removing asset dir"
    FileUtils.rm_rf(config.compiled_asset_dir)
    FileUtils.mkpath(config.compiled_asset_dir)
  end

  def generate_asset_files
    puts "Generating assets"
    run(*config.compile_assets_command_args)
  end

  def check_clean(fail_if_dirty, kind, solution, args)
    puts "Checking for #{kind} ..."
    files = `#{args.join(' ')}`.lines.map(&:chomp)
    result = $CHILD_STATUS.exitstatus
    abort "Error checking for #{kind} files" unless result.zero?

    message =
      if fail_if_dirty
        "Error: #{kind} files present: #{files.join(', ')}! #{solution}"
      else
        "Error: no new files/changes present! #{solution}"
      end

    ok = (fail_if_dirty == files.empty?)
    abort message unless ok
  end

  def check_modified_files
    kind = "modified/uncommitted changes"
    solution = "Either add+commit them first, or undo your changes with git checkout"
    args = %w(git diff-index --name-only HEAD)
    check_clean(true, kind, solution, args)
  end

  def check_untracked_files
    kind = "untracked changes"
    solution = "Either ignore them (gitignore) or remove them."
    args = %w(git ls-files --other --error-unmatch --exclude-standard)
    check_clean(true, kind, solution, args)
  end

  def check_unmodified_assets
    kind = "unmodified compiled assets"
    solution = "Did you really change anything? (The assets seem to not have changed since last time)."
    args = %w(git diff-index --name-only --cached HEAD)
    check_clean(false, kind, solution, args)
  end

  def commit_assets
    message = config.commit_message
    args = %W(git commit -m #{message})
    run(*args)
  end

  def add_asset_files
    puts "Adding asset files"
    args = %W(git add -fu #{config.compiled_asset_dir})
    run(*args)
  end

  def puts(message)
    STDOUT.puts(format(" >> %s ...", message))
  end
end

AssetCommit.new(MyConfig.new).commit