Issue 3498 - Improve file mapping / skipping logic

packagerSafari.py

 # coding: utf-8
 
 # This Source Code Form is subject to the terms of the Mozilla Public
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
 import os
 import re
 import json
 import ConfigParser
@@ skipping 210 matching lines @@
 
   params = {
     'type': type,
     'baseDir': baseDir,
     'releaseBuild': releaseBuild,
     'version': version,
     'devenv': devenv,
     'metadata': metadata,
   }
 
+  mapped = metadata.items('mapping') if metadata.has_section('mapping') else []
   files = Files(getPackageFiles(params), getIgnoredFiles(params),
                 process=lambda path, data: processFile(path, data, params))
-  if metadata.has_section('mapping'):
-    files.readMappedFiles(metadata.items('mapping'))
-  files.read(baseDir)
+  files.readMappedFiles(mapped)
+  files.read(baseDir, skip=[opt for opt, _ in mapped])
 
   if metadata.has_section('convert_js'):
     convertJS(params, files)
 
   if metadata.has_section('convert_img'):
     from imageConversion import convertImages
     convertImages(params, files)
 
   if metadata.has_section('preprocess'):
     files.preprocess(
@@ skipping 20 matching lines @@
   fixAbsoluteUrls(files)
 
   dirname = metadata.get('general', 'basename') + '.safariextension'
   for filename in files.keys():
     files[os.path.join(dirname, filename)] = files.pop(filename)
 
   if not devenv and keyFile:
     createSignedXarArchive(outFile, files, certs, key)
   else:
     files.zip(outFile)