fix parentheses when parsing multiple arguments

Apparently the busybox implementation of `base64` will line-wrap long output strings.
This meant that long username+password combinations could produce base64 that
contained spurious "\n" characters, which then led to:
```
2019/05/06 00:47:39 Unable to parse "/kaniko/.docker/config.json": invalid character '\n' in string literal
```

Fixed by just removing the newlines in base64 output.  A "better" solution would use a different base64
implementation that avoided line-wrapping in the first place.

Dockerfile

@@ -1,17 +1,11 @@
-FROM gcr.io/kaniko-project/executor:v0.7.0 AS kaniko
+FROM gcr.io/kaniko-project/executor:debug-v0.7.0
 
-FROM alpine:3.8
-
-# clone the official kaniko container into this one, env vars needs to be re-set
-COPY --from=kaniko / /
 ENV HOME /root
-ENV USER /root
+ENV USER root
 ENV SSL_CERT_DIR=/kaniko/ssl/certs
 ENV DOCKER_CONFIG /kaniko/.docker/
 ENV DOCKER_CREDENTIAL_GCR_CONFIG /kaniko/.config/gcloud/docker_credential_gcr_config.json
 
-RUN apk add --update --no-cache jq
-
 # add the wrapper which acts as a drone plugin
-COPY plugin.sh /usr/bin/
-ENTRYPOINT [ "/usr/bin/plugin.sh" ]
+COPY plugin.sh /kaniko/plugin.sh
+ENTRYPOINT [ "/kaniko/plugin.sh" ]

README.md

@@ -1,11 +1,34 @@
-# kaniko-plugin
+# drone-kaniko
 
 A thin shim-wrapper around the official [Google Kaniko](https://cloud.google.com/blog/products/gcp/introducing-kaniko-build-container-images-in-kubernetes-and-google-container-builder-even-without-root-access) Docker image to make it behave like the [Drone Docker plugin](http://plugins.drone.io/drone-plugins/drone-docker/).
 
+Example .drone.yml for Drone 1.0
+
+```yaml
+kind: pipeline
+name: default
+
+steps:
+- name: publish
+  image: banzaicloud/drone-kaniko
+  settings:
+    registry: registry.example.com
+    repo: registry.example.com/example-project
+    tags: ${DRONE_COMMIT_SHA}
+    cache: true
+    build_args:
+    - COMMIT_SHA=${DRONE_COMMIT_SHA}
+    - COMMIT_AUTHOR_EMAIL=${DRONE_COMMIT_AUTHOR_EMAIL}
+    username:
+      from_secret: docker-username
+    password:
+      from_secret: docker-password
+```
+
 ## Test that it can build
 
 ```bash
-docker run -it --rm -w /src -v $PWD:/src -e DOCKER_USERNAME=${DOCKER_USERNAME} -e DOCKER_PASSWORD=${DOCKER_PASSWORD} -e PLUGIN_REPO=banzaicloud/kaniko-plugin-test -e PLUGIN_TAGS=test -e PLUGIN_DOCKERFILE=Dockerfile.test banzaicloud/kaniko-plugin
+docker run -it --rm -w /src -v $PWD:/src -e PLUGIN_USERNAME=${DOCKER_USERNAME} -e PLUGIN_PASSWORD=${DOCKER_PASSWORD} -e PLUGIN_REPO=banzaicloud/drone-kaniko-test -e PLUGIN_TAGS=test -e PLUGIN_DOCKERFILE=Dockerfile.test banzaicloud/drone-kaniko
 ```
 
 ## Test that caching works
@@ -24,7 +47,7 @@ Add the following lines to plugin.sh's final command and build a new image from
 ```
 
 ```bash
-docker build -t banzaicloud/kaniko-plugin .
+docker build -t banzaicloud/drone-kaniko .
 ```
 
 
@@ -38,5 +61,5 @@ docker run -v $PWD:/cache gcr.io/kaniko-project/warmer:latest --image=alpine:3.8
 Run the builder on the host network to be able to access the registry:
 
 ```bash
-docker run --net=host -it --rm -w /src -v $PWD:/cache -v $PWD:/src -e DOCKER_USERNAME=${DOCKER_USERNAME} -e DOCKER_PASSWORD=${DOCKER_PASSWORD} -e PLUGIN_REPO=banzaicloud/kaniko-plugin-test -e PLUGIN_TAGS=test -e PLUGIN_DOCKERFILE=Dockerfile.test banzaicloud/kaniko-plugin
+docker run --net=host -it --rm -w /src -v $PWD:/cache -v $PWD:/src -e DOCKER_USERNAME=${DOCKER_USERNAME} -e DOCKER_PASSWORD=${DOCKER_PASSWORD} -e PLUGIN_REPO=banzaicloud/drone-kaniko-test -e PLUGIN_TAGS=test -e PLUGIN_DOCKERFILE=Dockerfile.test banzaicloud/drone-kaniko
 ```

plugin.sh

@@ -1,15 +1,17 @@
-#!/bin/sh
+#!/busybox/sh
 
 set -euo pipefail
 
 export PATH=$PATH:/kaniko/
 
-DOCKER_AUTH=`echo -n "${DOCKER_USERNAME}:${DOCKER_PASSWORD}" | base64`
+DOCKER_AUTH=`echo -n "${PLUGIN_USERNAME}:${PLUGIN_PASSWORD}" | base64 | tr -d "\n"`
+
+REGISTRY=${PLUGIN_REGISTRY:-https://index.docker.io/v1/}
 
 cat > /kaniko/.docker/config.json <<DOCKERJSON
 {
     "auths": {
-        "https://index.docker.io/v1/": {
+        "${REGISTRY}": {
             "auth": "${DOCKER_AUTH}"
         }
     }
@@ -17,13 +19,31 @@ cat > /kaniko/.docker/config.json <<DOCKERJSON
 DOCKERJSON
 
 DOCKERFILE=${PLUGIN_DOCKERFILE:-Dockerfile}
-DESTINATION=${PLUGIN_REPO}:${PLUGIN_TAGS:-latest}
 CONTEXT=${PLUGIN_CONTEXT:-$PWD}
 LOG=${PLUGIN_LOG:-info}
-BUILD_ARGS=`echo ${PLUGIN_BUILD_ARGS:-} | jq -r 'map("--build-arg " + .) | join(" ")'`
+
+if [[ -n "${PLUGIN_TARGET:-}" ]]; then
+    TARGET="--target=${PLUGIN_TARGET}"
+fi
+
+if [[ "${PLUGIN_CACHE:-}" == "true" ]]; then
+    CACHE="--cache=true"
+fi
+
+if [ -n "${PLUGIN_BUILD_ARGS:-}" ]; then
+    BUILD_ARGS=$(echo "${PLUGIN_BUILD_ARGS}" | tr ',' '\n' | while read build_arg; do echo "--build-arg=${build_arg}"; done)
+fi
+
+if [ -n "${PLUGIN_TAGS:-}" ]; then
+    DESTINATIONS=$(echo "${PLUGIN_TAGS}" | tr ',' '\n' | while read tag; do echo "--destination=${PLUGIN_REPO}:${tag} "; done)
+else
+    DESTINATIONS="--destination=${PLUGIN_REPO}:latest"
+fi
 
 /kaniko/executor -v ${LOG} \
-    --context ${CONTEXT} \
-    --dockerfile ${DOCKERFILE} \
-    --destination ${DESTINATION} \
-    ${BUILD_ARGS}
+    --context=${CONTEXT} \
+    --dockerfile=${DOCKERFILE} \
+    ${DESTINATIONS} \
+    ${CACHE:-} \
+    ${TARGET:-} \
+    ${BUILD_ARGS:-}