`-map_metadata:s:a -1` removes metadata other than audio

[powerman2206]

Summary + how to reproduce:

• run:

  ffmpeg -i input -map 0 -map_metadata:s:a -1 output
  

on an input with streams other than just audio

• version: git-2022-01-07-217c90a
• the issue here is that taking the input (and all its streams) and stripping what's supposed to be the audio streams' metadata actually strips all streams' metadata
• this brings up other issues that I'll probably put in another ticket
• here are the ffprobes of the example input and output after running the input through

  ffmpeg -i removing_wrong_metadata.mkv -map 0 -map -0:t -map_metadata:s:a -1 -c copy out.mkv
  

(-map -0:t required for the previous issue I mentioned)

input:

...
    Metadata:
      ENCODER         : Lavc58.134.100 libx264
      DURATION        : 00:01:29.509000000
  Stream #0:1(jpn): Audio: vorbis, 48000 Hz, stereo, fltp (default)
    Metadata:
      title           : Japanese 2.0
      ENCODER         : Lavc58.134.100 libvorbis
      DURATION        : 00:01:29.503000000
  Stream #0:2(eng): Subtitle: ass (default)
    Metadata:
      title           : English
      ENCODER         : Lavc58.134.100 ssa
      DURATION        : 00:00:00.000000000
...

output:

...
    Metadata:
      DURATION        : 00:01:29.508000000
  Stream #0:1: Audio: vorbis, 48000 Hz, stereo, fltp (default)
    Metadata:
      DURATION        : 00:01:29.503000000
  Stream #0:2: Subtitle: ass (default)
    Metadata:
      DURATION        : 00:00:00.000000000
...

• as can be seen, the metadata in the subtitle stream has been nuked even if it wasn't specified
• the same happens if -map_metadata 0 is specified before -map_metadata:s:a -1
• note: I also just noticed that the same happens when subtitle/video streams are specified in -map_metadata:s:X, so...

[powerman2206]

Just took the opening of Cowboy Bebop since it's the quickest thing I came up with that has all the required components. Might be a bit loud.