guide: document run-cache

[efiop]

So far affected commands are run/repro which create and/or use run cache. And push/pull/fetch/potentially status) that transfer (options for that are hidden for now) run cache to/from remote. Run cache is located in .dvc/cache/runs.

[efiop]

Will also need to update run-cache flags in run/repro to explain them through the run-cache concept.

[sarthakforwet]

Hey there I wanna work on this issue . Could you assign me this ?

[efiop]

Hi @sarthakforwet ! Thank you! But I don't think it is suitable for a contribution, as it is a WIP feature. Please check out need-help and good-first-issue labels, they should have something more suitable 🙂

[jorgeorpinel]

A suggested place to start is to add an "execution and reproduction" section to the dvc run cmd ref. similar to this: https://github.com/iterative/dvc.org/pull/1464/files

[jorgeorpinel]

More info that would be good to include for this ticket, from #1448 (comment):

1. Run-Cache can generate outputs in a suitable condition and that too indirectly (eg: only on run/repro), whereas a lockfile will always provide you with outputs without rerunning.
2. RunCache can generate lockfile. Even though you have a run-cache, you should still use lockfile because for the outputs.
3. get/import commands work well only if you have a lockfiile.

(Thanks @skshetry)

[jorgeorpinel]

Hello! So this continues to be a major discrepancy between released DVC and published docs. I know it's being worked on but at least basic mentions of this should exist in the docs for now. Is it still the plan for someone from engineering to submit a draft proposal adding such mentions? Thanks! Cc @efiop @shcheklein

[efiop]

@jorgeorpinel Likely no drafts until experiments are here or iterative/dvc#4223 .

[jorgeorpinel]

Hi @efiop! I'm finally finishing up some basic docs for this (sort of needed to doc dvc exp). Quick questions:

potentially status

1. status didn't end up working with the run-cache at all right?

2. dvc gc doesn't have a way to specifically DO, or DO NOT collect outputs referenced in the run-cache, right?

Thanks

[efiop]

1. Correct, not yet.

2. Correct.

[jorgeorpinel]

Feel free to reopen or make another issue if/when the run-cache implementation/terminology/etc change, or if more docs should be written. Thanks