CI: Caching

[niklasdewally]

Continue work done on #36, #37.

In short: we want to create a sensible caching scheme that allows all crates in this project to be cached, and updated as appropriate so that PRs do not need to clean build things. Some actions only use one crate, some use two, some use them all, so the caching needs to be invariant to this.

There were a few problems and approaches to these discussed in #36 #37.

[niklasdewally]

In particular, look at how conjure itself does it - it does
foo-hash-bar-hash-timestamp.

That way, you never need to delete then resave the cache as I do, you just make one with a newer timestamp and let github GC them all.

[ozgurakgun]

Caching isn't quite satisfactory at the moment, not entirely sure why.

PR #99 just failed to find a cache even though I just made small incremental changes.

See https://github.com/conjure-cp/conjure-oxide/actions/runs/6950773148/job/18911526725?pr=99

Cache not found for input keys: stable-Linux-gitmodules-e3b0c44298fc1c149afbf4c8996fb92427ae41e4-cargo-5ca8ee75eb05edfb53dc573ace4fa8a32bdee41b49119576a8e7952a62cabdda, stable-Linux-gitmodules-

I suggest (unless people see a reason not to do this)

• We do the timestamp based thing the previous comment alludes to
• We remove the full cache action, not sure if this is helping
• We could also introduce ccache, there is an action for it I use in conjure, in addition to caching cargo dirs

[niklasdewally]

Caching isn't quite satisfactory at the moment, not entirely sure why.

PR #99 just failed to find a cache even though I just made small incremental changes.

See https://github.com/conjure-cp/conjure-oxide/actions/runs/6950773148/job/18911526725?pr=99

Cache not found for input keys: stable-Linux-gitmodules-e3b0c44298fc1c149afbf4c8996fb92427ae41e4-cargo-5ca8ee75eb05edfb53dc573ace4fa8a32bdee41b49119576a8e7952a62cabdda, stable-Linux-gitmodules-

I suggest (unless people see a reason not to do this)

• We do the timestamp based thing the previous comment alludes to
• We remove the full cache action, not sure if this is helping
• We could also introduce ccache, there is an action for it I use in conjure, in addition to caching cargo dirs

I came across this before and was suspecting an emdash or something in the GitHub cache match somewhere - there's no reason why it shouldn't match as it currently is. Changing it entirely will be easier than debugging this I imagine

[niklasdewally]

@ozgurakgun seems to be fixed?