Try to fix push to DockerHub by extracting commands to a separate script

* https://docs.travis-ci.com/user/docker/#branch-based-registry-pushes

Signed-off-by: Graeme Watt <[email protected]>

.travis.yml

@@ -27,10 +27,7 @@ script:
 deploy:
   skip_cleanup: true
   provider: script
-  script: TAG_NAME="${TRAVIS_TAG:-latest}" && \
-          docker tag $IMAGE_NAME $IMAGE_NAME_REMOTE:$TAG_NAME && \
-          "docker login --password=$DOCKER_PASSWORD --username=$DOCKER_USERNAME" && \
-          docker push $IMAGE_NAME_REMOTE:$TAG_NAME
+  script: bash docker_push
   on:
     repo: HEPData/hepdata-converter-docker
     all_branches: true

docker_push

@@ -0,0 +1,5 @@
+#!/bin/bash
+TAG_NAME="${TRAVIS_TAG:-latest}"
+docker tag $IMAGE_NAME $IMAGE_NAME_REMOTE:$TAG_NAME
+echo "$DOCKER_PASSWORD" | docker login --username=$DOCKER_USERNAME --password-stdin
+docker push $IMAGE_NAME_REMOTE:$TAG_NAME