Allow commands with spaces to be constructed as new Commands

If you were using the `appraisal` executable and passed an argument that
contained spaces, those spaces would not be preserved when Appraisal
went to execute the full command. For instance, this command...

    appraisal 4.2 rspec spec/some/file_spec.rb -e "some example group"

*Should* be expanded as follows:

    BUNDLE_GEMFILE=$PWD/gemfiles/4.2.gemfile rspec spec/some/file_spec.rb -e "some example group"

...but before this commit would be incorrectly expanded as follows:

    BUNDLE_GEMFILE=$PWD/gemfiles/4.2.gemfile rspec spec/some/file_spec.rb -e some example group

Close thoughtbot#86

lib/appraisal/appraisal.rb

@@ -54,11 +54,18 @@ def write_gemfile
     end
 
     def install(job_size = 1)
-      Command.new(check_command + ' || ' + install_command(job_size)).run
+      command = [
+        check_command,
+        "||",
+        install_command(job_size)
+      ].flatten.join(" ")
+
+      Command.new(command).run
     end
 
     def update(gems = [])
-      Command.new(update_command(gems)).run
+      command, env = update_command(gems)
+      Command.new(command, env: env).run
     end
 
     def gemfile_path
@@ -83,17 +90,18 @@ def relativize
 
     def check_command
       gemfile_option = "--gemfile='#{gemfile_path}'"
-      ['bundle', 'check', gemfile_option].join(' ')
+      ['bundle', 'check', gemfile_option]
     end
 
     def install_command(job_size)
       gemfile_option = "--gemfile='#{gemfile_path}'"
-      ['bundle', 'install', gemfile_option, bundle_parallel_option(job_size)].compact.join(' ')
+      ['bundle', 'install', gemfile_option, bundle_parallel_option(job_size)].compact
     end
 
     def update_command(gems)
-      gemfile_config = "BUNDLE_GEMFILE='#{gemfile_path}'"
-      [gemfile_config, 'bundle', 'update', *gems].compact.join(' ')
+      env = { "BUNDLE_GEMFILE" => gemfile_path }
+      command = ['bundle', 'update', *gems].compact
+      [command, env]
     end
 
     def gemfile_root

lib/appraisal/cli.rb

@@ -86,10 +86,10 @@ def method_missing(name, *args, &block)
       matching_appraisal = File.new.appraisals.detect { |appraisal| appraisal.name == name.to_s }
 
       if matching_appraisal
-        Command.new(args.join(' '), matching_appraisal.gemfile_path).run
+        Command.new(args, gemfile: matching_appraisal.gemfile_path).run
       else
         File.each do |appraisal|
-          Command.new(ARGV.join(' '), appraisal.gemfile_path).run
+          Command.new(ARGV, gemfile: appraisal.gemfile_path).run
         end
       end
     end

lib/appraisal/command.rb

@@ -1,66 +1,85 @@
+require "shellwords"
+
 module Appraisal
   # Executes commands with a clean environment
   class Command
     BUNDLER_ENV_VARS = %w(RUBYOPT BUNDLE_PATH BUNDLE_BIN_PATH BUNDLE_GEMFILE).freeze
 
-    def self.from_args(gemfile)
-      ARGV.shift
-      command = ([$0] + ARGV).join(' ')
-      new(command, gemfile)
-    end
+    attr_reader :command, :env, :gemfile, :original_env
 
-    def initialize(command, gemfile = nil)
+    def initialize(command, options = {})
+      @gemfile = options[:gemfile]
+      @env = options.fetch(:env, {})
+      @command = command_starting_with_bundle(command)
       @original_env = {}
-      @gemfile = gemfile
-      if command =~ /^(bundle|BUNDLE_GEMFILE)/
-        @command = command
-      else
-        @command = "bundle exec #{command}"
-      end
     end
 
     def run
       announce
       with_clean_env do
-        unless Kernel.system(@command)
+        unless Kernel.system(env, command_as_string)
           exit(1)
         end
       end
     end
 
     def exec
       announce
-      with_clean_env { Kernel.exec(@command) }
+      with_clean_env { Kernel.exec(env, command_as_string) }
     end
 
     private
 
     def with_clean_env
       unset_bundler_env_vars
-      ENV['BUNDLE_GEMFILE'] = @gemfile
+      ENV['BUNDLE_GEMFILE'] = gemfile
       ENV['APPRAISAL_INITIALIZED'] = '1'
       yield
     ensure
       restore_env
     end
 
     def announce
-      if @gemfile
-        puts ">> BUNDLE_GEMFILE=#{@gemfile} #{@command}"
+      if gemfile
+        puts ">> BUNDLE_GEMFILE=#{gemfile} #{command_as_string}"
       else
-        puts ">> #{@command}"
+        puts ">> #{command_as_string}"
       end
     end
 
     def unset_bundler_env_vars
       BUNDLER_ENV_VARS.each do |key|
-        @original_env[key] = ENV[key]
+        original_env[key] = ENV[key]
         ENV[key] = nil
       end
     end
 
     def restore_env
-      @original_env.each { |key, value| ENV[key] = value }
+      original_env.each { |key, value| ENV[key] = value }
+    end
+
+    def command_starts_with_bundle?(original_command)
+      if original_command.is_a?(Array)
+        original_command.first =~ /^bundle/
+      else
+        original_command =~ /^bundle/
+      end
+    end
+
+    def command_starting_with_bundle(original_command)
+      if command_starts_with_bundle?(original_command)
+        original_command
+      else
+        %w(bundle exec) + original_command
+      end
+    end
+
+    def command_as_string
+      if command.is_a?(Array)
+        Shellwords.join(command)
+      else
+        command
+      end
     end
   end
 end

spec/acceptance/cli/run_spec.rb

@@ -14,6 +14,7 @@
 
     run 'appraisal install'
     write_file 'test.rb', 'puts "Running: #{$dummy_version}"'
+    write_file 'test with spaces.rb', 'puts "Running: #{$dummy_version}"'
   end
 
   it 'sets APPRAISAL_INITIALIZED environment variable' do
@@ -44,4 +45,12 @@
       expect(output).to include 'Running: 1.1.0'
     end
   end
+
+  context 'when one of the arguments contains spaces' do
+    it 'preserves those spaces' do
+      command = 'appraisal 1.0.0 ruby -rbundler/setup -rdummy "test with spaces.rb"'
+      output = run(command)
+      expect(output).to include 'Running: 1.0.0'
+    end
+  end
 end