save git hash to file during prepare step

.drone.yml

@@ -68,6 +68,7 @@ steps:
       - cd drone
       - LATEST_VERSION=$(git tag --sort v:refname | grep '^v[0-9]\{1,\}\.[0-9]\{1,\}\.[0-9]\{1,\}$' | tail -n 1)
       - git checkout $LATEST_VERSION
+      - printf $(git log -n 1 --pretty=%H) > ../commit_hash # we'll need this for the docker build
       - GOLANG_IMG=$(yq read .drone.yml 'steps[0].image')
       - docker pull $GOLANG_IMG
       - docker tag $GOLANG_IMG drone-builder:latest
@@ -95,12 +96,11 @@ steps:
     commands:
       - cd drone
       - rm .dockerignore
-      - COMMIT_HASH=$(git log -n 1 --pretty=%H)
       - >
         docker build 
         -f docker/Dockerfile.server.linux.amd64
         -t registry.jfmonty2.com/drone-server:latest 
-        --label drone_commit_hash=$COMMIT_HASH
+        --label drone_commit_hash=$(cat ../commit_hash)
         .
 
   - name: deploy