runner: add nodejs to job image; fetch-depth=0 for diff base

runner/compose.yml

@@ -3,7 +3,6 @@
 # is built reproducibly from runner/flake.nix — run `nix run .#load-image`
 # in this directory to load it into the host's Docker daemon before
 # starting the runner.
-version: "3.8"
 services:
   runner:
     image: docker.io/gitea/act_runner:nightly

runner/flake.nix

@@ -42,6 +42,7 @@
             curl
             jq
             tea
+            nodejs_20            # JS-based actions/checkout@v4 etc. need `node` on PATH
 
             cacert
             iana-etc
@@ -50,7 +51,7 @@
           # Skeleton filesystem layout: /tmp, /etc/passwd for nix,
           # writable nix store, cacert pointer.
           extraCommands = ''
-            mkdir -p tmp etc nix/var/{nix,log/nix} root
+            mkdir -p tmp etc/nix nix/var/{nix,log/nix} root
             chmod 1777 tmp
 
             cat > etc/passwd <<'EOF'