refactor(server): Use wrapper script to avoid path dependency

Instead of requiring the server component to be made aware of the
location of the Nix builder via environment variables, this commit
introduces a wrapper script for the builder that can simply exist on
the builders $PATH.

This is one step towards a slightly nicer out-of-the-box experience
when using `nix-build -A nixery-bin`.

1 files changed, 40 insertions, 0 deletions

diff --git a/tools/nixery/build-image/default.nix b/tools/nixery/build-image/default.nix
new file mode 100644
index 000000000000..4962e07deee9
--- /dev/null
+++ b/tools/nixery/build-image/default.nix
@@ -0,0 +1,40 @@
+# Copyright 2019 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# This file builds the tool used to calculate layer distribution and
+# moves the files needed to call the Nix builds at runtime in the
+# correct locations.
+
+{ buildGoPackage, lib, nix, writeShellScriptBin }:
+
+let
+  group-layers = buildGoPackage {
+    name = "group-layers";
+    goDeps = ./go-deps.nix;
+    src = ./.;
+
+    goPackagePath = "github.com/google/nixery/group-layers";
+
+    meta = {
+      description = "Tool to group a set of packages into container image layers";
+      license = lib.licenses.asl20;
+      maintainers = [ lib.maintainers.tazjin ];
+    };
+  };
+
+  # Wrapper script which is called by the Nixery server to trigger an
+  # actual image build.
+in writeShellScriptBin "nixery-build-image" ''
+  exec ${nix}/bin/nix-build --show-trace --no-out-link "$@" ${./build-image.nix}
+''