Add compat-option `no-keep-subs`

Closes #630

README.md

@@ -138,6 +138,7 @@ Some of yt-dlp's default options are different from that of youtube-dl and youtu
 * If `ffmpeg` is used as the downloader, the downloading and merging of formats happen in a single step when possible. Use `--compat-options no-direct-merge` to revert this
 * Thumbnail embedding in `mp4` is done with mutagen if possible. Use `--compat-options embed-thumbnail-atomicparsley` to force the use of AtomicParsley instead
 * Some private fields such as filenames are removed by default from the infojson. Use `--no-clean-infojson` or `--compat-options no-clean-infojson` to revert this
+* When `--embed-subs` and `--write-subs` are used together, the subtitles are written to disk and also embedded in the media file. You can use just `--embed-subs` to embed the subs and automatically delete the seperate file. See [#630 (comment)](https://github.com/yt-dlp/yt-dlp/issues/630#issuecomment-893659460) for more info. `--compat-options no-keep-subs` can be used to revert this.
 
 For ease of use, a few more compat options are available:
 * `--compat-options all`: Use all compat options

yt_dlp/YoutubeDL.py

@@ -404,7 +404,7 @@ class YoutubeDL(object):
     compat_opts:       Compatibility options. See "Differences in default behavior".
                        The following options do not work when used through the API:
                        filename, abort-on-error, multistreams, no-live-chat,
-                       no-clean-infojson, no-playlist-metafiles.
+                       no-clean-infojson, no-playlist-metafiles, no-keep-subs.
                        Refer __init__.py for their implementation
 
     The following parameters are not used by YoutubeDL itself, they are used by

yt_dlp/__init__.py

@@ -280,7 +280,7 @@ def _real_main(argv=None):
         'filename', 'format-sort', 'abort-on-error', 'format-spec', 'no-playlist-metafiles',
         'multistreams', 'no-live-chat', 'playlist-index', 'list-formats', 'no-direct-merge',
         'no-youtube-channel-redirect', 'no-youtube-unavailable-videos', 'no-attach-info-json',
-        'embed-thumbnail-atomicparsley', 'seperate-video-versions', 'no-clean-infojson',
+        'embed-thumbnail-atomicparsley', 'seperate-video-versions', 'no-clean-infojson', 'no-keep-subs',
     ]
     compat_opts = parse_compat_opts()
 
@@ -458,13 +458,13 @@ def _real_main(argv=None):
     if opts.addmetadata:
         postprocessors.append({'key': 'FFmpegMetadata'})
     if opts.embedsubtitles:
-        already_have_subtitle = opts.writesubtitles
+        already_have_subtitle = opts.writesubtitles and 'no-keep-subs' not in compat_opts
         postprocessors.append({
             'key': 'FFmpegEmbedSubtitle',
             # already_have_subtitle = True prevents the file from being deleted after embedding
             'already_have_subtitle': already_have_subtitle
         })
-        if not already_have_subtitle:
+        if not opts.writeautomaticsub and 'no-keep-subs' not in compat_opts:
             opts.writesubtitles = True
     # --all-sub automatically sets --write-sub if --write-auto-sub is not given
     # this was the old behaviour if only --all-sub was given.