Rename option to --thumbnail-format

yt_dlp/YoutubeDL.py

@@ -291,7 +291,7 @@ class YoutubeDL:
                        unless writeinfojson is also given
     writeannotations:  Write the video annotations to a .annotations.xml file
     writethumbnail:    Write the thumbnail image to a file
-    thumbnail_id:      ID of thumbnail to write
+    thumbnail_format:  Format code of thumbnail to write
     allow_playlist_files: Whether to write playlists' description, infojson etc
                        also to disk when using the 'write*' options
     write_all_thumbnails:  Write all thumbnail formats to files
@@ -2606,7 +2606,7 @@ class YoutubeDL:
 
     def _sort_thumbnails(self, thumbnails):
         thumbnails.sort(key=lambda t: (
-            t.get('id') == self.params.get('thumbnail_id') if t.get('id') is not None else False,
+            t.get('id') == self.params.get('thumbnail_format') if t.get('id') is not None else False,
             t.get('preference') if t.get('preference') is not None else -1,
             t.get('width') if t.get('width') is not None else -1,
             t.get('height') if t.get('height') is not None else -1,
@@ -2632,7 +2632,7 @@ class YoutubeDL:
                     continue
                 yield t
 
-        thumbnail_id = self.params.get('thumbnail_id')
+        thumbnail_id = self.params.get('thumbnail_format')
         if thumbnail_id and thumbnail_id not in [t.get('id') for t in thumbnails]:
             self.raise_no_formats(info_dict, msg=(
                 'Invalid thumbnail ID specified. '

yt_dlp/__init__.py

@@ -870,7 +870,7 @@ def parse_options(argv=None):
         'clean_infojson': opts.clean_infojson,
         'getcomments': opts.getcomments,
         'writethumbnail': opts.writethumbnail is True,
-        'thumbnail_id': opts.thumbnail_id,
+        'thumbnail_format': opts.thumbnail_format,
         'write_all_thumbnails': opts.writethumbnail == 'all',
         'writelink': opts.writelink,
         'writeurllink': opts.writeurllink,

yt_dlp/options.py

@@ -1525,9 +1525,9 @@ def create_parser():
         action='store_false', dest='writethumbnail',
         help='Do not write thumbnail image to disk (default)')
     thumbnail.add_option(
-        '--thumbnail-id',
-        metavar='ID', dest='thumbnail_id',
-        help='ID of thumbnail to write to disk')
+        '--thumbnail-format',
+        metavar='format', dest='thumbnail_format',
+        help='Format code of thumbnail to write to disk')
     thumbnail.add_option(
         '--write-all-thumbnails',
         action='store_const', dest='writethumbnail', const='all',