Tools
cargo-debstatus
Run in crate directory (alongside Cargo.toml) to check packaging status of dependencies.
See its section in Hacks.
bacon
Homepage, upstream repository.
Runs cargo check/clippy/test/run/etc. in the background, as you code. Customizable. Nice for patching, but beware, unless you install all the dependencies and replace source to them, it pulls from crates.io, which might be different with what's in Debian.
Packaged in unstable.
quilt
Patch management tool. Debian source format 3.0 is named after it (3.0 (quilt)
in debian/source/format).