[ENH] add `:auto-matching-tags` or `:auto-tags-regex`

[nickgarber]

:auto-tags
    This automatically groups items by all of their tags (i.e. items with exactly the same tags, in any order, will be grouped together).

Would love to have a version of the above that only groups on tags that match a regex. This would allow lots of nice structure, such as grouping agenda by project, (where projects tags follow the pattern P@.* or proj@.*) among other things.

[alphapapa]

Hi Nick,

Sure, that seems like a good idea. Would you be able to send a PR to implement this? I'd be glad to provide feedback as you develop it.

[nickgarber]

From what I understand the hierarchical scheme described in the documentation for Hierarchical Tags is not fully implemented, but this would produce some of the same effects.

[nickgarber]

Hi Nick,

Sure, that seems like a good idea. Would you be able to send a PR to implement this? I'd be glad to provide feedback as you develop it.

Yeah, for sure!

[nickgarber]

By the way, any preference for which name to use?

[alphapapa]

Seems like my email replies are not showing up on GitHub issues. :/

Anyway, I'd suggest :auto-tags-match, which is slightly more concise, and fits well with Emacs's regexp-matching terminology (e.g. string-match).