FR: Allow power search for "no" tag

[SBGit-2019]

It seems not possible to find items which have no tag set.

Ideas would be to allow either of these maybe - what is easiest to implement:

• tag="" (This search is accepted but does not return anything)
• !tag:* (with '*' to be expanded to all available tags, so not one of any available or similar)
• exist:tag (would require exist to work with multiple entries)

or similar.

[eikek]

You are right, this is not really possible to do right now.