Update README

README.md

@@ -1,26 +1,35 @@
 # scip-rust
 
-At the moment, this is just a tiny wrapper around `rust-analyzer` to generate SCIP data,
-with the configuration set up for use by Sourcegraph.
+A thin wrapper around `rust-analyzer scip`.
 
 ## Usage
 
-Install [`rust-analyzer`](https://rust-analyzer.github.io/book/installation.html) (any recent
-release works), make sure `cargo` and `rustc` are on `PATH`, then from the root of your
-workspace run:
+Make sure you have a working Rust toolchain (`cargo` and `rustc` on `PATH`) and
+[`rust-analyzer`] installed. Then, from the root of your workspace:
 
-```sh
+``` sh
 rust-analyzer scip .
 ```
 
-The [`scip-rust`](./scip-rust) script in this repo is the same one-liner with a few
-preflight checks; you can drop it into `PATH` if you prefer a stable command name.
+That's really all it does. The [`scip-rust`] script in this repo is the same
+command with a few preflight checks and toolchain fallbacks --- drop it into
+`PATH` if you want a stable command name.
 
-For CI, the `sourcegraph/scip-rust` Docker image bundles everything:
+### Docker
 
-```sh
+For CI, the `sourcegraph/scip-rust` image bundles everything:
+
+``` sh
 docker run --rm -v "$PWD:/work" sourcegraph/scip-rust
 ```
 
-If you want to upload LSIF to Sourcegraph.com in CI, check out
-[lsif-rust-action](https://github.com/sourcegraph/lsif-rust-action) instead.
+### Nix
+
+If you use Nix, run it straight from the flake:
+
+``` sh
+nix run github:sourcegraph/scip-rust
+```
+
+  [`rust-analyzer`]: https://rust-analyzer.github.io/book/installation.html
+  [`scip-rust`]: ./scip-rust