helix-term build: check git command's exit code

[the-mikedavis]

Noticed this when building with a derivation very similar to the one in nixpkgs (https://github.com/the-mikedavis/dotfiles/blob/4767713774fb87b369725585719c75c334ca92a0/overlays/helix.nix): the git hash comes out to the empty string 🤔. The next line takes a [..8] slice of the string so it ends up panicing.

In this case I think it makes sense to leave the revision out of the version string.

[archseer]

Weird, you'd think that git rev-parse would fail in that case.. There's no output at all?

[the-mikedavis]

Yeah seems like it's the empty string, must be something weird about how nix is setting up the git repository.

Maybe it's empty string if it's a bare repository? Or maybe nix might be mucking with the HEAD in a weird way 🤔

[the-mikedavis]

Oh actually since we're looking at the output of the Command it might be that the command is failing (I know this happens when the repository fails) and there's stuff on output.stderr. Maybe we should filter first on output.status.success()?

[the-mikedavis]

Seems like that was it ☝️

$ git init
$ git rev-parse HEAD
HEAD
fatal: ambiguous argument 'HEAD': unknown revision or path not in the working tree.
Use '--' to separate paths from revisions, like this:
'git <command> [<revision>...] -- [<file>...]'

Where HEAD\n endns up on stdout and the rest on stderr