Define Buildkite pipelines corresponding to git server hooks

I think maintaining a 1:1 correspondence with the git server hook makes sense
right now. Let's try it out!

ci/pipelines/briefcase.nix

@@ -1,17 +0,0 @@
-{ pkgs, ... }:
-
-let
-  pipeline.steps = [
-    {
-      key = "lint";
-      command = "${pkgs.git-secrets}/bin/git-secrets --scan-history";
-      label = ":broom: lint";
-    }
-    {
-      key = "build";
-      command = "nix-build . -I briefcase=$(pwd) --no-out-link --show-trace";
-      label = ":nix: build";
-      depends_on = "lint";
-    }
-  ];
-in pkgs.writeText "briefcase.yaml" (builtins.toJSON pipeline)

ci/pipelines/post-receive.nix

@@ -3,6 +3,12 @@
 let
   pipeline.steps = [
     {
+      key = "build-briefcase";
+      command = "nix-build . -I briefcase=$(pwd) --no-out-link --show-trace";
+      label = ":nix: build briefcase";
+    }
+    {
+      key = "build-socrates";
       command = ''
         nix-build '<nixpkgs/nixos>' \
           -I briefcase="$(pwd)" \
@@ -12,7 +18,8 @@ let
           --no-out-link \
           --show-trace
       '';
-      label = ":nix: build";
+      label = ":nix: build socrates";
+      depends_on = "build-briefcase";
     }
   ];
-in pkgs.writeText "socrates.yml" (builtins.toJSON pipeline)
+in pkgs.writeText "pipeline.yaml" (builtins.toJSON pipeline)

ci/pipelines/pre-receive.nix

@@ -0,0 +1,11 @@
+{ pkgs, ... }:
+
+let
+  pipeline.steps = [
+    {
+      key = "lint";
+      command = "${pkgs.git-secrets}/bin/git-secrets --scan-history";
+      label = ":broom: lint";
+    }
+  ];
+in pkgs.writeText "pipeline.yaml" (builtins.toJSON pipeline)