Split video by chapters (#158)

* New options `--split-chapters` and `--no-split-chapters`
* The output/path of the split files can be given using the key `chapter`
* Additional keys `section_title`, `section_number`, `section_start`, `section_end` are available in the output template
* Alias `--split-tracks` for parity with animelover/youtube-dl
* `--sponskrub-cut` and `--split-chapter` cannot work together

Closes:
https://github.com/blackjack4494/yt-dlc/issues/277
https://github.com/ytdl-org/youtube-dl/issues/28438
https://github.com/ytdl-org/youtube-dl/issues/12907
https://github.com/ytdl-org/youtube-dl/issues/6480
https://github.com/ytdl-org/youtube-dl/pull/25005

Rewritten from the implementation by: femaref and Wattux
https://github.com/Wattux/youtube-dl/tree/split-at-timestamps
https://github.com/ytdl-org/youtube-dl/pull/25005
https://github.com/femaref/youtube-dl/tree/split-track

yt_dlp/__init__.py

@@ -279,9 +279,14 @@ def _real_main(argv=None):
 
     def report_conflict(arg1, arg2):
         write_string('WARNING: %s is ignored since %s was given\n' % (arg2, arg1), out=sys.stderr)
+
     if opts.remuxvideo and opts.recodevideo:
         report_conflict('--recode-video', '--remux-video')
         opts.remuxvideo = False
+    if opts.sponskrub_cut and opts.split_chapters and opts.sponskrub is not False:
+        report_conflict('--split-chapter', '--sponskrub-cut')
+        opts.sponskrub_cut = False
+
     if opts.allow_unplayable_formats:
         if opts.extractaudio:
             report_conflict('--allow-unplayable-formats', '--extract-audio')
@@ -371,11 +376,7 @@ def _real_main(argv=None):
         })
         if not already_have_thumbnail:
             opts.writethumbnail = True
-    # XAttrMetadataPP should be run after post-processors that may change file
-    # contents
-    if opts.xattrs:
-        postprocessors.append({'key': 'XAttrMetadata'})
-    # This should be below all ffmpeg PP because it may cut parts out from the video
+    # This should be below most ffmpeg PP because it may cut parts out from the video
     # If opts.sponskrub is None, sponskrub is used, but it silently fails if the executable can't be found
     if opts.sponskrub is not False:
         postprocessors.append({
@@ -386,6 +387,11 @@ def _real_main(argv=None):
             'force': opts.sponskrub_force,
             'ignoreerror': opts.sponskrub is None,
         })
+    if opts.split_chapters:
+        postprocessors.append({'key': 'FFmpegSplitChapters'})
+    # XAttrMetadataPP should be run after post-processors that may change file contents
+    if opts.xattrs:
+        postprocessors.append({'key': 'XAttrMetadata'})
     # ExecAfterDownload must be the last PP
     if opts.exec_cmd:
         postprocessors.append({