old_contents: from __future__ import print_function, unicode_literals
  
  import json
  import os
  import os.path as path
  import shutil
  import subprocess
  import sys
  import tarfile
  from time import time
  import urllib
  
  from mach.registrar import Registrar
  from mach.decorators import (
      CommandArgument,
      CommandProvider,
      Command,
  )
  
  from servo.command_base import CommandBase
  
  @CommandProvider
  class MachCommands(CommandBase):
      @Command('cargo',
               description='Run Cargo',
               category='devenv',
               allow_all_args=True)
      @CommandArgument('params', default=None, nargs='...',
                       help="Command-line arguments to be passed through to Cargo")
      def run(self, params):
          return subprocess.call(["cargo"] + params,
                                 env=self.build_env())
  
new_contents: from __future__ import print_function, unicode_literals
  
  import json
  import os
  import os.path as path
  import shutil
  import subprocess
  import sys
  import tarfile
  from time import time
  import urllib
  
  from mach.registrar import Registrar
  from mach.decorators import (
      CommandArgument,
      CommandProvider,
      Command,
  )
  
  from servo.command_base import CommandBase
  
  @CommandProvider
  class MachCommands(CommandBase):
      @Command('cargo',
               description='Run Cargo',
               category='devenv',
               allow_all_args=True)
      @CommandArgument('params', default=None, nargs='...',
                       help="Command-line arguments to be passed through to Cargo")
      def run(self, params):
          return subprocess.call(["cargo"] + params,
                                 env=self.build_env())
  
      @Command('rustc',
               description='Run the Rust compiler',
               category='devenv',
               allow_all_args=True)
      @CommandArgument('params', default=None, nargs='...',
                       help="Command-line arguments to be passed through to rustc")
      def run(self, params):
          return subprocess.call(["rustc"] + params, env=self.build_env())
  
subject: Add a `mach rustc` command