ci: some speedups for slow tests

Hi,

I was staring at CI way more often recently, and that got me annoyed real fast because it's just painstakingly slow. So I decided to have a look and try do something about it, the result of which is this patch series.

The series contains a couple of bits that are specific to GitLab, and a couple of fixes that are generic. Some highlights:

• Installing the Git for Windows SDK speeds up from 3 minutes to 10 seconds by using tar(1) instead of Extract-Archive.

• t0027 speeds up from >10 minutes to 6 minutes on Windows by avoiding the overhead of spawning redundant processes.

• t5551 and t5559 both speed up by a factor of 10 on macOS, going from 20 minutes each to 2 minutes each by using reftables in a repo with 100k refs.

• "fedora-breaking-changes-meson" speeds up by a factor of 2, going from 35 minutes to 16 minutes. Turns out our SHA256 implementation is quite slow with "-O0".

Unfortunately, our Windows runners at GitLab are still atrociously slow by themselves. So the critical path only improves by about ~10 minutes, going from 60-70 minutes to 55 minutes end-to-end. But hey, at least the other jobs now give feedback a bit faster.

Thanks!

Patrick

To: git@vger.kernel.org Cc: Johannes Schindelin Johannes.Schindelin@gmx.de

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