Cleanup dev setup (#36)

* chore: nixfmt-rfc-style

* tidy: don't need old nixpkgs for ocamlformat any more

* tidy: nixpkgs rather than dev opam scope for lsp/utop

* bump: nixpkgs version for format check

* refactor(build): onix based env

.github/workflows/main.yaml

@@ -35,4 +35,4 @@ jobs:
     - name: Checkout
       uses: actions/checkout@v4
     - uses: cachix/install-nix-action@v26
-    - run: nix-shell -I nixpkgs=channel:nixos-23.05 --pure -p ocamlformat_0_22_4 dune_3 ocaml --run "dune build @fmt"
+    - run: nix-shell -I nixpkgs=channel:nixpkgs-unstable --pure -p ocamlformat_0_22_4 dune_3 ocaml --run "dune build @fmt"

Makefile

@@ -18,3 +18,8 @@ opam-install-deps:
 
 format:
 	dune build @fmt --auto-promote
+
+onix-lock:
+	onix lock ./gcloud.opam ./gcloud-cli.opam --resolutions="ocaml-system=5.2.0" --lock-file ./onix-lock.json
+	onix lock ./gcloud.opam ./gcloud-cli.opam ./gcloud-melange.opam --resolutions="ocaml-system=5.2.0" --with-dev-setup=true --with-test=true --lock-file ./onix-lock-dev.json
+	git add onix-lock.json onix-lock-dev.json

README.md

@@ -1,2 +1,21 @@
 OCaml bindings to the Google Cloud Platform APIs
 ================================================
+
+## Development
+
+The default nix devShell will have the packages needed to develop `ocaml-gcloud`:
+```
+nix develop '.#' # (or use nix-direnv)
+dune build ...
+```
+
+### Updating opam package set
+
+If you've updated the `.opam` files in the project and need to recalculate the `opam` deps, run `make onix-lock` and refresh the devShell:
+
+```
+# From inside the nix devShell
+$ make onix-lock
+$ exit # (or nix-direnv-reload if using nix-direnv)
+$ nix develop '.#'
+```