Bug 1291910 - Add ability for mach eslint to accept --fix. r=Felipe

MozReview-Commit-ID: 5PB2oI2jPri

--HG--
extra : rebase_source : 42d03b9ab93c4ef390d0dfa59d25dd330309071d

tools/lint/mach_commands.py

@@ -86,8 +86,10 @@ class MachCommands(MachCommandBase):
                      help='Filename extensions to lint, default: "[.js,.jsm,.jsx,.xml,.html]".')
     @CommandArgument('-b', '--binary', default=None,
                      help='Path to eslint binary.')
+    @CommandArgument('--fix', default=False, action='store_true',
+                     help='Request that eslint automatically fix errors, where possible.')
     @CommandArgument('args', nargs=argparse.REMAINDER)  # Passed through to eslint.
-    def eslint(self, setup, ext=None, binary=None, args=None):
+    def eslint(self, setup, ext=None, binary=None, fix=False, args=None):
         '''Run eslint.'''
 
         module_path = self.get_eslint_module_path()
@@ -148,6 +150,10 @@ class MachCommands(MachCommandBase):
                     '--ext', ext,  # This keeps ext as a single argument.
                     ] + args
 
+        # eslint requires that --fix be set before the --ext argument.
+        if fix:
+            cmd_args.insert(1, '--fix')
+
         success = self.run_process(
             cmd_args,
             pass_thru=True,  # Allow user to run eslint interactively.