Cargo Git configuration improvements

[dominic-mulligan-arm]

Configured Cargo to:

• Use the Git command line tool rather than the Rust libgit2 library,
• Retry all network attempts 3 times.

[egrimley-arm]

There's an RFC, at least, for sharing stuff between Cargo.toml files, but I don't think it's been implemented yet, unfortunately: rust-lang/cargo#8415

[nspin]

I think this is actually a .cargo/config option:

https://doc.rust-lang.org/cargo/reference/config.html#net

I think we'll only need to include it once, just in the top-level .cargo/config:

https://doc.rust-lang.org/cargo/reference/config.html#hierarchical-structure

[dominic-mulligan-arm]

Ah, that makes more sense than amending every Cargo.toml file. I'll push a change in a bit.

[egrimley-arm]

So I tried putting the git-fetch-with-cli in veracruz/.cargo/config and running cargo clean; cargo build in sdk/freestanding-execution-engine, and it made no difference, though the config was parsed because I got a warning when I deliberately mistyped the thing.

When I say it made no difference I mean the script called git that was on my path got executed just two times, with the arguments rev-parse HEAD, in each case, with or without the config change. Also I didn't seen any signs of git being invoked when I tried strace -f -o log.

What am I doing wrong?

[egrimley-arm]

What I'm doing wrong is not deleting the cache from my ~/.cargo/!

[egrimley-arm]

It now seems to work, though the retry = 3 probably won't make it retry git or cause git to retry. But presumably it doesn't hurt, either.

[egrimley-arm]

Conclusion: Just add the three lines to veracruz/.cargo/config instead.

[dominic-mulligan-arm]

OK, done!

[dominic-mulligan-arm]

+1+1 = +1 reached, merging.