Enable Cargo's sparse protocol in CI

[ehuss]

This enables the sparse protocol in CI in order to exercise and dogfood it. This is intended test the production server in a real-world situation.

Closes #107342

[rustbot]

r? @pietroalbini

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[jyn514]

Thanks! r=me with or without the nit addressed :)

[jyn514]

Hmm, why does this need to be set both here and in the ci.yml file? I would expect it to only need to be set here.

[ehuss]

The environment isn't inherited inside Docker images. I could use the --env flag to forward it, but I felt less confident that would cover everything.

[jyn514]

Hmm, I still see "updating crates.io index" in the build logs. Is that expected?

https://github.com/rust-lang/rust/actions/runs/4060238532/jobs/6989128411#step:26:1096

[ehuss]

Yes. With the sparse protocol, Cargo still needs to download registry index files covering the dependencies that are needed. That's what the Updating crates.io index line is referring to.

[jyn514]

👍

@bors r+ rollup=iffy

[bors]

📌 Commit 5e90940 has been approved by jyn514

It is now in the queue for this repository.

[bors]

⌛ Testing commit 5e90940 with merge 5d32458...

[bors]

☀️ Test successful - checks-actions
Approved by: jyn514
Pushing 5d32458 to master...

[rust-timer]

Finished benchmarking commit (5d32458): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-6.4%	[-6.4%, -6.4%]	1
All ❌✅ (primary)	-	-	0

Cycles

This benchmark run did not return any relevant results for this metric.