change travis to use nightly tag for dockerhub (#12)

Author: dgrove-oss

.travis.yml

@@ -25,7 +25,7 @@ deploy:
     repo: apache/incubator-openwhisk-runtime-rust
 - provider: script
   skip_cleanup: true
-  script: "./tools/travis/publish.sh openwhisk rust1.34 latest"
+  script: "./tools/travis/publish.sh openwhisk rust1.34 nightly"
   on:
     branch: master
     repo: apache/incubator-openwhisk-runtime-rust

tools/travis/publish.sh

@@ -35,8 +35,8 @@ TERM=dumb ./gradlew \
 -PdockerImagePrefix=${IMAGE_PREFIX} \
 -PdockerImageTag=${IMAGE_TAG}
 
-  # if doing latest also push a tag with the hash commit
-  if [ ${IMAGE_TAG} == "latest" ]; then
+  # if doing nightly also push a tag with the hash commit
+  if [ ${IMAGE_TAG} == "nightly" ]; then
   SHORT_COMMIT=`git rev-parse --short HEAD`
   TERM=dumb ./gradlew \
   :${RUNTIME}:distDocker \