Yes, this would be extremely useful to preserve ReplayGain tags!

If you're transferring tickets from the old tracker please close the old ones as duplicates and comment on them with a link back here.

http://bugs.musicbrainz.org/ticket/5509 (Clear existing tags on if not tagged by MB)
http://bugs.musicbrainz.org/ticket/4678 (Preserve replaygain tags)

^^ both have relevant discussion of requirements for this enhancement.

I wrote a patch to address the "exclude some tags from being cleared" issue. What do you think?

I was thinking more of a checkbox form, but that's a nice start, too.
If we have to do it this way, I'd still like to have a list of tags for reference somewhere.
Keep up the good work!

Well, the problem with checkboxes is that the UI gets very complicated (many, many tags). Also, with checkboxes it is not possible to exclude completely custom tags from being cleared. This UI has the benefit of being very simple, while pretty powerful at the same time.

A comprehensive list of tags is here: http://musicbrainz.org/doc/MusicBrainz_Picard/Tags/Mapping

I do like the textfield option, as it allows custom tags. One suggestion I have would be to allow using at least one wildcard_character: *. Useful (at least) for replaygain tags.

Yes, this is a good idea! I will implement this!

I created a new branch on my github fork, which also has the patches for PICARD-146, PICARD-148 and bitmap's tagdiff branch merged in: https://github.com/weisslj/picard/tree/PICARD-19-test. It would be cool if you could test it .

Now that tagdiff is in mainline picard, it gives an obvious way forward to fix this: Either a right-click option or a checkbox next to each listed tag, "Don't clear this tag"

In review at https://github.com/musicbrainz/picard/pull/30

The "Don't clear this tag" right click option could be easily implemented on top of this (just append it to the text field). I think the text field is required still, otherwise it is not possible to prevent tags from clearing without having a file that has these tags.

FWIW, a right click option would give me the impression it would only apply to the selected files and not permanently.

Yes... it could maybe be fixed by using a phrase like "Permanently prevent this tag from being cleared or overwritten with MusicBrainz data". But better make a new ticket for it...

Marko Sultsing: I left out the wildcard thing that was present in PICARD-19-test since I'm not anymore sure it is what people really want. It is not very probably, but I would want to strip "replaygain_blabla_gain", but keep "replaygain_album_gain", so I would never use the wildcard character. Also, wildcards make it more difficult to parse the string if we want to have something like the "right-click to ignore tags permanently thing".

I'm marking this as "solved", since my solution is now in the master branch. For any specific enhancement, please open a new ticket (and link it to this!).