Introduce --keep-fragments

youtube_dl/options.py

@@ -468,6 +468,10 @@ def parseOpts(overrideArguments=None):
         '--abort-on-unavailable-fragment',
         action='store_false', dest='skip_unavailable_fragments',
         help='Abort downloading when some fragment is not available')
+    downloader.add_option(
+        '--keep-fragments',
+        action='store_true', dest='keep_fragments', default=False,
+        help='Keep downloaded fragments on disk after downloading is finished; fragments are erased by default')
     downloader.add_option(
         '--buffer-size',
         dest='buffersize', metavar='SIZE', default='1024',