Add dynamic ref evaluation support to plan import

[kkaarreell]

No description provided.

[kkaarreell]

This should address #1832
I will also add a test for this feature later.

[kkaarreell]

One more thing I didn't like is the lack of information about the imported plan. I have added a commit improving this a bit, although I am really not sure the approach is correct (definitely not pretty).
The output looks like this.

    /plans/dynamic-ref
        discover
            how: fmf
            order: 50
            imported-url: https://github.com/teemtee/tmt
            imported-ref: fedora
            imported-path: /tests/discover/data
            imported-name: /plans/fmf/exclude
            directory: /var/tmp/tmt/run-344/import/plans/dynamic-ref/tests/discover/data
            summary: 2 tests selected
                /tests/discover2
                /tests/discover3

[kkaarreell]

Hi @psss @happz @thrix ,
I have forced pushed a new version (since there were a lot of changes in main in the meantime), trying to follow the proposed approach.
What is not yet addressed:

• the code branch # Use fmf cache for exploring plans (the whole git repo is not needed) where I am not sure what would be the right approach.. I guess I will wait for tmt tests to fail to see what is the impact
• adding tests for this new functionality

[kkaarreell]

I have added back the test update so now there will be failures due to the newly added warning.
@psss you were suggesting to print the warning only for tmt plan show, how do I find out how tmt has been issued?

[kkaarreell]

OK, I did one more updated, adding extra git clone when we don't have enough data to evaluate dynamic ref. Still, it may be handy to avoid doing this when we do not need those data. WDYT about it?

[psss]

Thanks for addressing comments, looks good. I've rebased on the latest main and added just a couple of minor changes in f9dcd90.

Outdated.