Push to 3.8 tag, not latest

Waiting on https://github.com/docker-library/official-images/pull/4501

.drone.yml

@@ -4,7 +4,7 @@ pipeline:
     volumes: [ '/var/run/docker.sock:/var/run/docker.sock' ]
     repo: alpine-dev
     build_args:
-      - ALPINE_TAG=${ALPINE_TAG%%,*}
+      - ALPINE_TAG=3.8
 
   test:
     image: docker
@@ -14,22 +14,13 @@ pipeline:
 
   publish:
     image: spritsail/docker-publish
-    when: { branch: [ master ], event: [ push, tag, deployment ] }
+    when: { branch: [ 3.8 ], event: [ push, tag, deployment ] }
     volumes: [ '/var/run/docker.sock:/var/run/docker.sock' ]
     secrets: [ docker_username, docker_password, microbadger_token ]
     from: alpine-dev
-    repo: 'spritsail/alpine'
-    tags: ${ALPINE_TAG}
+    repo: 'spritsail/alpine:3.8'
 
   notify:
     image: spritsail/notify
     when: { status: [ success, failure ] }
     secrets: [ webhook_url, notify_token ]
-
-matrix:
-  ALPINE_TAG:
-    - 3.4
-    - 3.5
-    - 3.6
-    - 3.7,latest
-    - edge

Dockerfile

@@ -1,7 +1,17 @@
 ARG SU_EXEC_VER=v0.3
-ARG ALPINE_TAG=3.7
+ARG ALPINE_TAG=3.8
 
-FROM alpine:$ALPINE_TAG
+FROM alpine:3.7 AS upgrade
+
+ARG ALPINE_TAG
+RUN sed -i "s/3\.7/${ALPINE_TAG}/g" /etc/apk/repositories \
+ && apk --no-cache upgrade
+
+# ~~~~~~~~~~~~~~~~~~~~~~
+
+FROM scratch
+
+COPY --from=upgrade / /
 
 ARG SU_EXEC_VER
 ARG ALPINE_TAG