FolderNameFilter: allow multiple tags per folder

[mjg]

So far, the last entry wins when a folder is specified multiple times as a folder transform. The reason is that the folder name is a key in a dict whose values are tags. On the other hand, if a message has copies in several folders then all these rules apply.

Change (fix?) afew's FolderNameFilter so that multiple transforms for the same folder lead to multiple tags being added. Technically, this is done by using sets as values in the transform dict.

In the future, we might think about implementing notmuch-tag style notation (with the obvious quoting issues).

[mjg]

FTR: CI runs stone age notmuch (0.29) against py 3.12 which is doomed to fail. The fix for ConfigParser in py 3.12 is in the latest notmuch 0.38 only.

[GuillaumeSeren]

Hey @mjg
Thank you for this patch.

I feel this use case is a bit unclear to me, can you detail a bit how this could append ?

[mjg]

Hey @mjg Thank you for this patch.

I feel this use case is a bit unclear to me, can you detail a bit how this could append ?

Sure, I didn't meet my own standard on commit messages, sorry :-)

Here's the why: Say, I have accounts Work and Pleasure whose mail ends up in subdirs of directories Work and Pleasure (not that some work couldn't be pleasure, but ...). I want to tag mail by account (for easy display), but also tag sent mail as sent even with clients which just put sent mail in the Sent folder. Thus, my afew config is:

[FolderNameFilter]
folder_explicit_list = Work/Sent Pleasure/Sent
folder_transforms = Work/Sent:Work Work/Sent:sent Pleasure/Sent:Pleasure Pleasure/Sent:sent

and of course more for other folders.
If we had notmuch style config, I would say Work/Sent:"+Work +sent" Pleasure/Sent:"+Pleasure +sent", but we don't, that's why two rules are needed.

I know the account tag search is equivalent to a path search, but the tag is nice with clients which display it; besides, I can remove/replace the tag and have the MailMover move mail between accounts.