The problem here was two fold:
1. the folder "/target/" would be top-level of the repo only, it should be "target/" to properly exclude target folders anywhere in the repo
2. the default Rust/Cargo folder when compiling code is "debug/", which gets used perhaps more often that "target/", added that
See the [official recommendation](http://doc.crates.io/guide.html#cargotoml-vs-cargolock)
> * If you're building a library, put Cargo.lock in your .gitignore.
> * If you're building an executable, check Cargo.lock into git.
Ryan Scott