Make subtitles easier to obtain

[forthrin]

Right now, including subtitles in downloaded videos comes off as rather complicated and longhand:

youtube-dl -f mp4 --all-subs --embed-subs --convert-subtitles srt $URL

One option for wanting subtitles to begin with, one to embed them, and one to force the necessary format for the container. (VLC does not support ttml, possibly in the 3.0 release which seems to take aeons).

Possible suggestions:

1. Make --embed-subs imply --all-subs, and automatically convert subtitles to the necessary format without having to specify it manually.
2. Create a magical shorthand option (like --cc or --st) that does the same as above (basically saying: I want subtitles, just make it happen).

A side note: --convert-subtitles should be called --convert-subs to consistent with other options.

~$ youtube-dl --help | grep -i subtitle
--write-sub                      Write subtitle file
--write-auto-sub                 Write automatically generated subtitle file (YouTube only)
--all-subs                       Download all the available subtitles of the video
--list-subs                      List all available subtitles for the video
--sub-format FORMAT              Subtitle format, accepts formats preference, for example: "srt" or
--sub-lang LANGS                 Languages of the subtitles to download (optional) separated by commas,
--embed-subs                     Embed subtitles in the video (only for mkv and mp4 videos)
--convert-subtitles FORMAT       Convert the subtitles to other format (currently supported:
~$ 

[dstftw]

1. Those should not be mixed since --all-subs may involve additional network I/O. How is it supposed to know which subtitles format you want? You specify it youself in --convert-subtitles.
2. I'd prefer not to duplicate options.

[dstftw]

--convert-subs shorthand works as well.

[dstftw]

You can put these options in config if you don't want to type them all the time.