Add a which-part-provided command or output (behind a flag)

[Nish Aravamudan]

As discussed with kyrofa on IRC, it would be very helpful to query snapcraft for which part is responsible for a path in a snap.

Additionally, perhaps hidden behind a flag, it would be very helpful for new (or optimizing) snappers to be able to have snapcraft list all files in the snap due to each part. This would be used, for instance, to determine what paths can be removed from stage/prime/etc in the YAML, as they might be unused, but the part to modify is not immediately obvious.

[Sergio Schvezov (sergiusens)]

Kyrofa can you add more detail?

[Kyle Fazzari (kyrofa)]

This idea was borne out of debugging git-ubuntu, where we found multiple versions of the same library and were uncertain which part was providing which library. Snapcraft already knows this information thanks to state tracking, it would be pretty cool to expose that to the end user. Still need to figure out what this looks like, though.

[Kyle Fazzari (kyrofa)]

Proposal is here: https://forum.snapcraft.io/t/proposal-snapcraft-provides/5275

[Kyle Fazzari (kyrofa)]

Proposed solution is here: https://github.com/snapcore/snapcraft/pull/2121

[Kyle Fazzari (kyrofa)]

Another rendition: https://github.com/snapcore/snapcraft/pull/2184