Initial commit: syncronize a single file

.gitignore

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+tmp
+.swo
+*~
+*.swp
+

bin/trout

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+#!/usr/bin/env ruby
+
+require 'trout'
+Trout::CLI.run(ARGV)
+

features/support/env.rb

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+require 'rubygems'
+require 'aruba'
+require 'fileutils'
+
+Before do
+  FileUtils.rm_rf("tmp")
+  FileUtils.mkdir("tmp")
+end
+
+PROJECT_ROOT = File.expand_path(File.join(File.dirname(__FILE__), '..', '..')).freeze
+BIN_PATH = File.join(PROJECT_ROOT, 'bin').freeze
+LIB_PATH = File.join(PROJECT_ROOT, 'lib').freeze
+
+ENV['PATH'] = [BIN_PATH, ENV['PATH']].join(':')
+ENV['RUBYLIB'] = LIB_PATH

features/sync_gemfile.feature

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+Feature: sync a Gemfile between two repositories
+
+  @puts @announce
+  Scenario: sync a Gemfile
+    Given a directory named "upstream_repo"
+    And a directory named "child_repo"
+    And a file named "upstream_repo/Gemfile" with:
+      """
+      source "http://rubygems.org"
+      gem "rails"
+      gem "mysql"
+      """
+    When I cd to "upstream_repo"
+    And I run "git init"
+    And I run "git add Gemfile"
+    And I run "git commit -m 'Added gemfile'"
+    And I cd to "../child_repo"
+    And I run "trout checkout Gemfile ../upstream_repo"
+    And I run "cat Gemfile"
+    Then the output should contain:
+      """
+      source "http://rubygems.org"
+      gem "rails"
+      gem "mysql"
+      """
+    When I cd to "../upstream_repo"
+    And I write to "Gemfile" with:
+      """
+      source "http://rubygems.org"
+      gem "rails"
+      gem "postgresql"
+      """
+    When I run "git add Gemfile"
+    And I run "git commit -m 'Changed to postgres'"
+    And I cd to "../child_repo"
+    When I append to "Gemfile" with:
+      """
+
+      gem "redcloth"
+      """
+    When I run "trout update Gemfile"
+    And I run "cat Gemfile"
+    Then the output should contain:
+      """
+      source "http://rubygems.org"
+      gem "rails"
+      <<<<<<< Gemfile
+      gem "mysql"
+      gem "redcloth"
+      =======
+      gem "postgresql"
+      >>>>>>> .trout/upstream
+      """
+

lib/trout.rb

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+require 'trout/cli'
+

lib/trout/cli.rb

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+require 'trout/managed_file'
+
+module Trout
+  class CLI
+    def self.run(arguments)
+      new(arguments).run
+    end
+
+    attr_reader :arguments, :git_url, :filename, :file, :command
+
+    def initialize(arguments)
+      self.arguments = arguments
+      self.file = ManagedFile.new(filename)
+    end
+
+    def run
+      case command
+      when 'checkout'
+        self.git_url = arguments[2]
+        file.copy_from(git_url)
+      when 'update'
+        file.update
+      end
+    end
+
+    private
+
+    def arguments=(arguments)
+      @arguments    = arguments
+      self.command  = arguments[0]
+      self.filename = arguments[1]
+    end
+
+    attr_writer :git_url, :filename, :file, :command
+  end
+end

lib/trout/managed_file.rb

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+require 'fileutils'
+require 'trout/version_list'
+
+module Trout
+  class ManagedFile
+    attr_reader :filename, :checked_out_url
+
+    def initialize(filename)
+      @filename = filename
+    end
+
+    def copy_from(git_url)
+      checkout(git_url)
+      copy_to_destination
+      write_url_and_version
+    ensure
+      cleanup
+    end
+
+    def update
+      checkout(previous_git_url)
+      merge_to_destination
+    ensure
+      cleanup
+    end
+
+    private
+
+    def checkout(git_url)
+      run_or_fail("git clone #{git_url} #{working('git')}")
+      @checked_out_url = git_url
+    end
+
+    def copy_to_destination
+      FileUtils.cp(working('git', filename), filename)
+    end
+
+    def merge_to_destination
+      upstream       = working('upstream')
+      at_last_update = working('at_last_update')
+      merge          = working('merge')
+
+      FileUtils.cp(working('git', filename), upstream)
+
+      checkout_last_version
+      FileUtils.cp(working('git', filename), at_last_update)
+
+      enforce_newline(upstream)
+      enforce_newline(at_last_update)
+      enforce_newline(filename)
+
+      run("diff3 -mX #{filename} #{at_last_update} #{upstream} > #{merge}")
+      FileUtils.mv(merge, filename)
+    ensure
+      FileUtils.rm_rf(upstream)
+      FileUtils.rm_rf(at_last_update)
+    end
+
+    def cleanup
+      FileUtils.rm_rf(working('git'))
+      @checked_out_url = nil
+    end
+
+    def prepare_working_directory
+      FileUtils.mkdir(working_root)
+    end
+
+    def working_root
+      '.trout'
+    end
+
+    def write_url_and_version
+      version_list.update(filename,
+                          'git_url' => checked_out_url,
+                          'version' => checked_out_version)
+    end
+
+    def checked_out_version
+      git_command("rev-parse HEAD")
+    end
+
+    def checkout_last_version
+      git_command("checkout #{previous_git_version}")
+    end
+
+    def git_command(command)
+      run_or_fail("git --git-dir=#{working('git/.git')} --work-tree=#{working('git')} #{command}").strip
+    end
+
+    def previous_git_url
+      version_list.git_url_for(filename)
+    end
+
+    def previous_git_version
+      version_list.version_for(filename)
+    end
+
+    def version_list
+      @version_list ||= VersionList.new(working('versions'))
+    end
+
+    def working(*paths)
+      File.join(working_root, *paths)
+    end
+
+    def enforce_newline(path)
+      if IO.read(path)[-1].chr != "\n"
+        File.open(path, "a") { |file| file.puts }
+      end
+    end
+
+    def run(command)
+      `#{command} 2>&1`
+    end
+
+    def run_or_fail(command)
+      output = run(command)
+      unless $? == 0
+        raise "Command failed with status #{$?}:\n#{command}\n#{output}"
+      end
+      output
+    end
+  end
+end

lib/trout/version_list.rb

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+require 'yaml'
+
+module Trout
+  class VersionList
+    attr_reader :path, :entries
+
+    def initialize(path)
+      @path = path
+    end
+
+    def git_url_for(filename)
+      read
+      entries[filename]['git_url']
+    end
+
+    def version_for(filename)
+      read
+      entries[filename]['version']
+    end
+
+    def update(filename, info)
+      read
+      entries[filename] ||= {}
+      entries[filename].update(info)
+      write
+    end
+
+    private
+
+    def read
+      if File.exist?(path)
+        @entries = YAML.load(IO.read(path))
+      else
+        @entries = {}
+      end
+    end
+
+    def write
+      File.open(path, 'w') do |file|
+        file.write(YAML.dump(entries))
+      end
+    end
+  end
+end