Update readme with installation and configuration instructions. (#12)

README.md

@@ -1,15 +1,62 @@
 # Docker Registry Artifact plugin
 
-This is merely a skeleton plugin that plugin developers can fork to get quickly
-started with writing artifact plugins for GoCD.
+The docker registry artifact plugin provides a way to push and pull docker images on GoCD 
+
+## Building the code base
+
+To build the jar, run `./gradlew clean test assemble`
 
 ## Getting started
 
-* Coming soon
+### Requirements
 
-## Building the code base
+- GoCD Server 18.7+
+- Docker registry
+- Docker daemon
 
-To build the jar, run `./gradlew clean test assemble`
+### Installation
+
+Build the plugin with `./gradlew clean test assemble`
+
+Copy the file build/libs/docker-registry-artifact-plugin-VERSION.jar to the GoCD server under ${GO_SERVER_DIR}/plugins/external and restart the server. The GO_SERVER_DIR is usually /var/lib/go-server on Linux and C:\Program Files\Go Server on Windows.
+
+### Configuration
+
+There are three levels of configuration needed in order for publishing and fetching a docker image as an artifact.
+
+#### Configure the Artifact Store
+
+1. Login to GoCD server as admin and navigate to Admin > Artifact Stores
+2. Click on `Add` to add the store details for the plugin.
+   - Specify the store id
+   - Choose the docker registry artifact plugin
+   - Specify the `Docker Registry Url`
+   - Specify `username` and `password`
+
+   ![](images/artifact_store.png)
+
+#### Publish artifact config
+
+1. Navigate to the `Artifacts` tab under Stage > Job
+2. Choose artifact type `External`
+   - Specify the `artifact id`.
+   - Specify the `store id` of an existing artifact store
+3. Configure the build specific artifact details.
+   - Optionally specify the `Image` and `Tag`. Usually, the `Tag` can be an environment variable that changes for every build. For example, the `GO_PIPELINE_LABEL` can be used to publish a versioned docker image.
+   - Optionally specify the `BuildFile`. Specify a json file name. The format of the file should be `{"image": "name", "tag": "tag pattern"}`. The `BuildFile` option can be used if the `Tag` option cannot be specified for the tag pattern you want to use. The generation of this json file must be handled within the GoCD job.
+
+   ![](images/build_and_publish_image_artifacts.png)
+
+#### Fetch artifact config
+
+To pull an image from an upstream pipeline or stage, the following information is required:
+
+1. Specify a `Pipeline Dependency` material if you have an upstream pipeline you want to pull the docker image.
+2. Navigate to `Tasks` tab under Stage > Job
+3. Add a `Fetch Artifact` task
+   -  Choose artifact origin type `External`
+   - Specify the pipeline, stage and job name.
+   - Specify the artifact id of the external artifact that belongs to the upstream job
 
 ## License
 
@@ -31,7 +78,7 @@ limitations under the License.
 
 ## About the license and releasing your plugin under a different license
 
-The skeleton code in this repository is licensed under the Apache 2.0 license. The license itself specifies the terms
+The code in this repository is licensed under the Apache 2.0 license. The license itself specifies the terms
 under which derivative works may be distributed (the license also defines derivative works). The Apache 2.0 license is a
 permissive open source license that has minimal requirements for downstream licensors/licensees to comply with.