mbsync: add timid flag

[Duncaen]

Description

Fixes #4250. Adds the --timid flag to the mbsync command/plugin.

To Do

• Documentation.
• Changelog.
• Tests.

[JOJ0]

@Duncaen this looks pretty straightforward, and I'll look at it soon. Can you provide an example in action in the meantime before I try it out myself - just for a high-level usability check?

[Duncaen]

At the moment its just the normal mbsync output with a prompt after printing all the album changes. I've experimented with different output formats using the same format as the import process, but it hides a lot of information and therefor doesn't really show what is changing for most of the fields like credits since the only visible fields in the import process are titles, track numbers and selected album related information.

% beet mbsync -t album:"12 Bar Bruise"
King Gizzard & the Lizard Wizard - 12 Bar Bruise
  albumartist_credit:  -> King Gizzard & the Lizard Wizard
  albumartists_sort:  -> King Gizzard & the Lizard Wizard
  albumartists_credit:  -> King Gizzard & the Lizard Wizard
  release_group_title:  -> 12 Bar Bruise
  language:  -> eng
  albumstatus: official -> Official
King Gizzard & the Lizard Wizard - 12 Bar Bruise - Elbow
  work:  -> Elbow
  mb_workid:  -> 817d206e-6e1e-419b-90e7-3b4ff5b038da
  artists_sort:  -> King Gizzard & the Lizard Wizard
  artists_credit:  -> King Gizzard & the Lizard Wizard
  lyricist:  -> Stu Mackenzie
  composer:  -> Stu Mackenzie
  composer_sort:  -> Mackenzie, Stu
  artist_credit:  -> King Gizzard & the Lizard Wizard
  data_source: MusicBrainz
  track_alt: 1
King Gizzard & the Lizard Wizard - 12 Bar Bruise - Muckraker
  work:  -> Muckraker
  mb_workid:  -> e5e5aa72-35c8-46c6-9f9e-30c54028532b
  artists_sort:  -> King Gizzard & the Lizard Wizard
  artists_credit:  -> King Gizzard & the Lizard Wizard
  lyricist:  -> Stu Mackenzie
  composer:  -> Stu Mackenzie
  composer_sort:  -> Mackenzie, Stu
  artist_credit:  -> King Gizzard & the Lizard Wizard
  data_source: MusicBrainz
  track_alt: 2
King Gizzard & the Lizard Wizard - 12 Bar Bruise - Nein
  work:  -> Nein
  mb_workid:  -> 9066a7c3-a2f5-4d0f-94f1-0802cfbca7bb
  artists_sort:  -> King Gizzard & the Lizard Wizard
  artists_credit:  -> King Gizzard & the Lizard Wizard
  lyricist:  -> Stu Mackenzie
  composer:  -> Stu Mackenzie
  composer_sort:  -> Mackenzie, Stu
  artist_credit:  -> King Gizzard & the Lizard Wizard
  data_source: MusicBrainz
  track_alt: 3
King Gizzard & the Lizard Wizard - 12 Bar Bruise - 12 Bar Bruise
  work:  -> 12 Bar Bruise
  mb_workid:  -> 085f84e1-b6e2-4933-9167-0f3a5538de25
  artists_sort:  -> King Gizzard & the Lizard Wizard
  artists_credit:  -> King Gizzard & the Lizard Wizard
  lyricist:  -> Stu Mackenzie
  composer:  -> Stu Mackenzie
  composer_sort:  -> Mackenzie, Stu
  artist_credit:  -> King Gizzard & the Lizard Wizard
  data_source: MusicBrainz
  track_alt: 4
King Gizzard & the Lizard Wizard - 12 Bar Bruise - Garage Liddiard
  work:  -> Garage Liddiard
  mb_workid:  -> db56a592-5af0-4a44-a25e-dbe4735f4202
  artists_sort:  -> King Gizzard & the Lizard Wizard
  artists_credit:  -> King Gizzard & the Lizard Wizard
  lyricist:  -> Stu Mackenzie
  composer:  -> Stu Mackenzie
  composer_sort:  -> Mackenzie, Stu
  artist_credit:  -> King Gizzard & the Lizard Wizard
  data_source: MusicBrainz
  track_alt: 5
King Gizzard & the Lizard Wizard - 12 Bar Bruise - Sam Cherry’s Last Shot
  work:  -> Sam Cherry’s Last Shot
  mb_workid:  -> e352079e-b6ab-41c8-bbed-e8825ebfa7ee
  artists_sort:  -> King Gizzard & the Lizard Wizard
  artists_credit:  -> King Gizzard & the Lizard Wizard
  lyricist:  -> Stu Mackenzie
  composer:  -> Stu Mackenzie
  composer_sort:  -> Mackenzie, Stu
  artist_credit:  -> King Gizzard & the Lizard Wizard
  data_source: MusicBrainz
  track_alt: 6
King Gizzard & the Lizard Wizard - 12 Bar Bruise - High Hopes Low
  work:  -> High Hopes Low
  mb_workid:  -> 3ba5a0f2-8387-4602-b1b2-d1e5b81cbc7e
  artists_sort:  -> King Gizzard & the Lizard Wizard
  artists_credit:  -> King Gizzard & the Lizard Wizard
  lyricist:  -> Stu Mackenzie
  composer:  -> Stu Mackenzie
  track_alt: 5
King Gizzard & the Lizard Wizard - 12 Bar Bruise - Sam Cherry’s Last Shot
  work:  -> Sam Cherry’s Last Shot
  mb_workid:  -> e352079e-b6ab-41c8-bbed-e8825ebfa7ee
  artists_sort:  -> King Gizzard & the Lizard Wizard
  artists_credit:  -> King Gizzard & the Lizard Wizard
  lyricist:  -> Stu Mackenzie
  composer:  -> Stu Mackenzie
  composer_sort:  -> Mackenzie, Stu
  artist_credit:  -> King Gizzard & the Lizard Wizard
  data_source: MusicBrainz
  track_alt: 6
King Gizzard & the Lizard Wizard - 12 Bar Bruise - High Hopes Low
  work:  -> High Hopes Low
  mb_workid:  -> 3ba5a0f2-8387-4602-b1b2-d1e5b81cbc7e
  artists_sort:  -> King Gizzard & the Lizard Wizard
  artists_credit:  -> King Gizzard & the Lizard Wizard
  lyricist:  -> Stu Mackenzie
  composer:  -> Stu Mackenzie
  composer_sort:  -> Mackenzie, Stu
  artist_credit:  -> King Gizzard & the Lizard Wizard
  data_source: MusicBrainz
  track_alt: 7
King Gizzard & the Lizard Wizard - 12 Bar Bruise - Cut Throat Boogie
  work:  -> Cut Throat Boogie
  mb_workid:  -> ae782e3f-8bfb-4264-a1a0-fec89da99b22
  artists_sort:  -> King Gizzard & the Lizard Wizard
  artists_credit:  -> King Gizzard & the Lizard Wizard
  artist_credit:  -> King Gizzard & the Lizard Wizard
  data_source: MusicBrainz
  track_alt: 8
King Gizzard & the Lizard Wizard - 12 Bar Bruise - Bloody Ripper
  work:  -> Bloody Ripper
  mb_workid:  -> acca11f9-8e95-4dc0-95c0-1a45a309e74e
  artists_sort:  -> King Gizzard & the Lizard Wizard
  artists_credit:  -> King Gizzard & the Lizard Wizard
  lyricist:  -> Stu Mackenzie
  composer:  -> Stu Mackenzie
  composer_sort:  -> Mackenzie, Stu
  artist_credit:  -> King Gizzard & the Lizard Wizard
  data_source: MusicBrainz
  track_alt: 9
King Gizzard & the Lizard Wizard - 12 Bar Bruise - Uh Oh, I Called Mum
  work:  -> Uh Oh, I Called Mum
  mb_workid:  -> 36d0d9ed-a3c4-407f-ab7e-592279daea83
  artists_sort:  -> King Gizzard & the Lizard Wizard
  artists_credit:  -> King Gizzard & the Lizard Wizard
  lyricist:  -> Stu Mackenzie
  composer:  -> Stu Mackenzie
  composer_sort:  -> Mackenzie, Stu
  artist_credit:  -> King Gizzard & the Lizard Wizard
  data_source: MusicBrainz
  track_alt: 10
King Gizzard & the Lizard Wizard - 12 Bar Bruise - Sea of Trees
  work:  -> Sea of Trees
  mb_workid:  -> 6b406af4-9508-4d58-a565-6961e42dc54b
  artists_sort:  -> King Gizzard & the Lizard Wizard
  artists_credit:  -> King Gizzard & the Lizard Wizard
  lyricist:  -> Stu Mackenzie
  composer:  -> Stu Mackenzie
  composer_sort:  -> Mackenzie, Stu
  artist_credit:  -> King Gizzard & the Lizard Wizard
  data_source: MusicBrainz
  track_alt: 11
King Gizzard & the Lizard Wizard - 12 Bar Bruise - Footy Footy
  work:  -> Footy Footy
  mb_workid:  -> 4a5eccd4-b99c-4093-bffa-95626214f199
  artists_sort:  -> King Gizzard & the Lizard Wizard
  artists_credit:  -> King Gizzard & the Lizard Wizard
  artist_credit:  -> King Gizzard & the Lizard Wizard
  data_source: MusicBrainz
  track_alt: 12

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