Nightly fails to build unless git is installed

[jbeich]

Regressed by #59303. Source archives don't have .git subdirectory, so missing git executable shouldn't be fatal.

thread 'main' panicked at 'Command::new("git").args(&["rev-parse", "--verify",
                           &format!("@:./{}" ,
                                    submodule)]).current_dir(&builder.src).output() failed with No such file or directory (os error 2)', src/bootstrap/native.rs:82:26

http://beefy9.nyi.freebsd.org/data/112amd64-default/497233/logs/errors/rust-nightly-1.35.0.20190330_1.log

[Mark-Simulacrum]

cc @euclio and @cuviper

It might be worth just always rebuilding in source archives -- it seems reasonable to assume most people aren't editing the code in those. Unsure though; perhaps that's not a correct assumption.

[cuviper]

It might be worth just always rebuilding in source archives

Yes, that was the intention, which you can see in the else case after checking git_output.status.success(). But I guess missing git entirely fails sooner, in the Command::output() call.

[cuviper]

Perhaps we should be using GitInfo::new for this, which has conditions for ignoring git or missing .git. That would also return the current actual hash in that path, which is probably even better to use than the submodule recorded in rust's HEAD (@:./path) or index (:./path).

[cuviper]

Actually, the Build already contains in_tree_llvm_info and emscripten_llvm_info!

[euclio]

Thanks for the quick fix!