Factor out file history lookup into AsyncFileLogJob

[cruessler]

This PR partly addresses #1115. As of 2022-08-03, it is still a draft.

It changes the following:

• It factors out getting commit info into AsyncFileLogJob. It does not move getting commit info into a worker thread.

I followed the checklist:

• [ ] I added unittests
• [ ] I ran make check without errors
• [ ] I tested the overall application
• [ ] I added an appropriate item to the changelog

[cruessler]

@extrawurst Currently, components can use AsyncLog::get_slice to get a slice of the revlog even if it has not been fully read yet. In this PR, I want to first implement the existing functionality using AsyncJob, so it seems I would need something similar to get_slice. Is that assumption correct? If so, can this be done using AsyncJob? There is set_progress, but I’m not sure whether this is the right function to use. I’m even starting to wonder whether my overall approach is correct.

[extrawurst]

the AsyncLog specific do not have to be squeezed into the trait functions run/progress. check out AsyncSyntaxJob::result it is not part of the generic interface and can be used specific to the use case. Not sure this answers your question. WDYT?

[stale[bot]]

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