add folder include mechanism

[petri]

I have only a few folders I want to archive, among many. So I would propose adding an "include" mechanism in addition to the current exclude-based one. I can contribute that. Would the following be ok:

• user can either include or exclude folders, not both
• if neither is used, all folders are selected

[apaku]

I think having an either-or is too surprising. All other tools I know that have include/exclude have a defined override rule, i.e. either an include overrides excludes matching the same tag or vice-versa.

I didn't need include rules myself since I only wanted to exclude one tag recursively and another one non-recursively, but I wouldn't mind having include support.

[petri]

Ok. I don't have a strong opinion either way, just thought either-or would be simpler for users - and I don't need the extra use case coverage that an override rule brings. I do like the idea though.