chore: attempt to use S3 as the container cache.

.dockerignore

@@ -0,0 +1 @@
+.docker-build-cache

.drone.yml

@@ -3,29 +3,36 @@ type: docker
 name: default
 
 steps:
+- name: retrieve build cache
+  image: meltwater/drone-cache
+  pull: true
+  environment:
+    AWS_ACCESS_KEY_ID:
+      from_secret: ACCESS_KEY_ID
+    AWS_SECRET_ACCESS_KEY:
+      from_secret: SECRET_ACCESS_KEY
+    AWS_PLUGIN_PATH_STYLE: true
+  settings:
+    restore: true
+    endpoint:
+      from_secret: S3_ENDPOINT
+    bucket:
+      from_secret: CACHE_BUCKET
+    region: us-east-1
+    path-style: true
+    mount: .docker-build-cache
+
 - name: build 
   image: thegeeklab/drone-docker-buildx:23
   privileged: true
-  when:
-    ref:
-    - refs/heads/main
-  environment:
-    ACCESS_KEY_ID:
-      from_secret: ACCESS_KEY_ID
-    SECRET_ACCESS_KEY:
-      from_secret: SECRET_ACCESS_KEY
-    S3_ENDPOINT:
-      from_secret: S3_ENDPOINT  
-    CACHE_BUCKET:
-      from_secret: CACHE_BUCKET
   settings:
     username: james
     password:
       from_secret: REGISTRY_TOKEN
     registry: code.harton.nz
     repo: code.harton.nz/james/asdf_container
-    cache_to: code.harton.nz/james/asdf_container:cache
-    cache_from: code.harton.nz/james/asdf_container:cache
+    cache_from: 'type=local\\,src=.docker-build-cache'
+    cache_to: 'type=local,dest=.docker-build-cache'
     provenance: false
     tags:
     - latest
@@ -33,3 +40,21 @@ steps:
     - linux/arm64
     - linux/amd64
 
+- name: store build cache
+  image: meltwater/drone-cache
+  pull: true
+  environment:
+    AWS_ACCESS_KEY_ID:
+      from_secret: ACCESS_KEY_ID
+    AWS_SECRET_ACCESS_KEY:
+      from_secret: SECRET_ACCESS_KEY
+    AWS_PLUGIN_PATH_STYLE: true
+  settings:
+    rebuild: true
+    endpoint:
+      from_secret: S3_ENDPOINT
+    bucket:
+      from_secret: CACHE_BUCKET
+    region: us-east-1
+    path-style: true
+    mount: .docker-build-cache