Add functional but preliminary channel tab support

Add channel tabs to the channel template and script
Update continuation token to request different tabs

Add support for 'reelItemRenderer' format required to extract shorts

youtube/yt_data_extract/common.py

@@ -249,6 +249,9 @@ def extract_item_info(item, additional_info={}):
     primary_type = type_parts[-2]
     if primary_type == 'video':
         info['type'] = 'video'
+    elif type_parts[0] == 'reel': # shorts
+        info['type'] = 'video'
+        primary_type = 'short'
     elif primary_type in ('playlist', 'radio', 'show'):
         info['type'] = 'playlist'
         info['playlist_type'] = primary_type
@@ -343,6 +346,48 @@ def extract_item_info(item, additional_info={}):
         else:
             info['index'] = None
 
+    elif primary_type == 'short':
+        info['id'] = item.get('videoId')
+        if not info['id']:
+            info['id'] = deep_get(item,'navigationEndpoint',
+                                  'reelWatchEndpoint', 'videoId')
+        info['approx_view_count'] = extract_approx_int(item.get('viewCountText'))
+
+        # handle case where it is "No views"
+        if not info['approx_view_count']:
+            if ('No views' in item.get('shortViewCountText', '')
+                    or 'no views' in accessibility_label.lower()):
+                info['view_count'] = 0
+                info['approx_view_count'] = '0'
+
+        # dig into accessibility data to get duration for shorts
+        accessibility_label = multi_deep_get(item,
+            ['accessibility', 'accessibilityData', 'label'],
+            default='')
+
+        duration = re.search(r'(\d+) (second|seconds|minute) - play video',
+                             accessibility_label)
+        if duration.group(2) == 'minute':
+            info['duration'] = "1:00"
+        else:
+            info['duration'] = "0:" + duration.group(1).zfill(2)
+
+        # if it's an item in a playlist, get its index
+        if 'index' in item: # url has wrong index on playlist page
+            info['index'] = extract_int(item.get('index'))
+        elif 'indexText' in item:
+            # Current item in playlist has ▶ instead of the actual index, must
+            # dig into url
+            match = re.search(r'index=(\d+)', deep_get(item,
+                'navigationEndpoint', 'commandMetadata', 'webCommandMetadata',
+                'url', default=''))
+            if match is None:   # worth a try then
+                info['index'] = extract_int(item.get('indexText'))
+            else:
+                info['index'] = int(match.group(1))
+        else:
+            info['index'] = None
+
     elif primary_type in ('playlist', 'radio'):
         info['id'] = item.get('playlistId')
         info['video_count'] = extract_int(item.get('videoCount'))
@@ -398,6 +443,8 @@ _item_types = {
     'gridVideoRenderer',
     'playlistVideoRenderer',
 
+    'reelItemRenderer',
+
     'playlistRenderer',
     'compactPlaylistRenderer',
     'gridPlaylistRenderer',