Add commit information to roc versions built from source

[Hasnep]

Addresses #7030.

I'm not that experienced with Rust and I'm not familiar with the style and priorities of the Roc compiler team, so I'd appreciate feedback on anything that looks out of place or inefficient 😅

I think this is nearly done, but I'm getting a default commit timestamp when I run it locally:

roc built from commit 6d0a9b69d, committed at 1980-01-01T00:00:00.000000000Z

I think it's a default timestamp, maybe for reproducible builds? But that doesn't make sense to me because it's not a build timestamp, it's a commit timestamp 🤔

Again, any help is appreciated! 😀

[Hasnep]

Just left some comments explaining my changes

[Anton-4]

Thanks for helping out @Hasnep!

What do you think about calling git using Command?
We like to avoid extra dependencies (like vergen-gitcl) when we can.

[Hasnep]

What do you think about calling git using Command? We like to avoid extra dependencies (like vergen-gitcl) when we can.

Nice, this is something I considered but wasn't sure about, so I just used a package for the initial version, I'll switch to using Command, thanks :)

[Hasnep]

@Anton-4 I've removed vergen as a dependency and now directly call the git CLI to get the latest commit's information. The output works as expected now:

❱ cargo run -- --version
roc built from commit db485ad90, committed at 2024-09-12 10:46:45
❱ cargo run -- version
roc built from commit db485ad90, committed at 2024-09-12 10:46:45

and when the repo has changes:

❱ cargo run -- version
roc built from commit db485ad90 with changes, committed at 2024-09-12 10:46:45

Let me know if you think there's anything that I can improve :)

[Hasnep]

Thanks for your comments @Anton-4, I've addressed them all now 👍

[lukewilliamboswell]

This will be really useful. Thank you @Hasnep

[Anton-4]

To fix the test failures you'll need to do cargo fmt --all and for the nix-build failure I recommend printing git_show_output, perhaps there is some useful stderr about why the timestamp is not there...

[Hasnep]

The nix-build is failing because Nix filters out .git and other VCS related files from builds to try and make them more reproducible. I've looked a bit into how I can override this behaviour, but Nix is not documented very well :/

[Anton-4]

but Nix is not documented very well :/

Yes, that is true 😅

I think instead of panicking with "Failed to parse timestamp as an integer" we could default to the string "missing timestamp", that would be most inline with the nix philosophy vs trying to work around this.

[Hasnep]

I've added a check to see if the .git/HEAD file exists before trying to run any git commands, nix build now runs on my laptop and running the built binary prints roc built from source.