Add inputs and examples to readme

Signed-off-by: Nick Adcock <nick.adcock@docker.com>

README.md

@@ -1,2 +1,190 @@
 # build-push-action
-Build+push official Docker GitHub action
+
+Builds and pushes docker images and will log in to a docker registry if required
+
+[Inputs](#Inputs)
+* [repository](#repository)
+* [username](#username)
+* [password](#password)
+* [registry](#registry)
+* [tags](#tags)
+* [tag_with_ref](#tag_with_ref)
+* [tag_with_sha](#tag_with_sha)
+* [path](#path)
+* [dockerfile](#dockerfile)
+* [target](#target)
+* [always_pull](#always_pull)
+* [build_args](#build_args)
+* [labels](#labels)
+* [add_git_labels](#add_git_labels)
+* [push](#push)
+
+[Example usage](#Example-usage)
+
+## Inputs
+
+### `repository`
+
+**Required** Docker repository to tag the image with.
+
+### `username`
+
+Username used to log in to a docker registry. If not set then no login will occur.
+
+### `password`
+
+Password used to log in to a docker registry. If not set then no login will occur.
+
+### `registry`
+
+Server address of docker registry. If not set then will default to Docker Hub.
+
+### `tags`
+
+Comma-delimited list of tags. These will be added to the registry/repository to form the image's tags.
+
+Example:
+
+```yaml
+tags: tag1,tag2
+```
+
+### `tag_with_ref`
+
+Boolean value. Defaults to `false`.
+
+Automatically tags the built image with the git reference. The format of the tag depends on the type of git reference with all forward slashes replaced with `-`.
+
+For pushes to a branch the reference will be `refs/heads/{branch-name}` and the tag will be `{branch-name}`. If `{branch-name}` is master then the tag will be `latest`.
+
+For pull requests the reference will be `refs/pull/{pull-request}` and the tag will be `pr-{pull-request}`.
+
+For git tags the reference will be `refs/tags/{git-tag}` and the tag will be `{git-tag}`.
+
+Examples:
+
+|Git Reference|Image tag|
+|---|---|
+|`refs/heads/master`|`latest`|
+|`refs/heads/my/branch`|`my-branch`|
+|`refs/pull/2/merge`|`pr-2-merge`|
+|`refs/tags/v1.0.0`|`v1.0.0`|
+
+### `tag_with_sha`
+
+Boolean value. Defaults to `false`.
+
+Automatically tags the built image with the git short sha prefixed with `sha-`.
+
+Example:
+
+|Git sha|Image tag|
+|---|---|
+|`676cae2f85471aeff6776463c72881ebd902dcf9`|`sha-676cae2`|
+
+### `path`
+
+Path to run the docker build from. Defaults to `.`.
+
+### `dockerfile`
+
+Name of the Dockerfile (Default is 'path/Dockerfile'). Defaults to `{path}/Dockerfile`.
+
+### `target`
+
+Sets the target build stage to build.
+
+### `always_pull`
+
+Boolean value. Defaults to `false`.
+
+Always attempt to pull a newer version of the image.
+
+### `build_args`
+
+Comma-delmited list of build-time variables.
+
+Example:
+
+```yaml
+build_args: arg1=value1,arg2=value2
+```
+
+### `labels`
+
+Comma-delimited list of labels to add to the built image.
+
+Example:
+
+```yaml
+labels: label_name_1=label_value_1,label_name_2=label_value_2
+```
+
+### `add_git_labels`
+
+Boolean value. Defaults to `false`.
+
+Adds labels with git repo info to the built image.
+
+The labels are:
+
+|Label key|Example value|Description|
+|---|---|---|
+|`com.docker.github-actions-actor`|`my-username`|The actor that kicked off the workflow. For example this could be the username of the user that did the git push.|
+|`com.docker.github-actions-sha`|`676cae2f85471aeff6776463c72881ebd902dcf9`|Full git sha of the current commit.|
+
+
+### `push`
+
+Boolean value. Defaults to `true`.
+
+Whether to push the built image.
+
+## Example usage
+
+The following will build the root Dockerfile, tag the image as `myorg/myrepository:latest`, logs in to docker hub using GitHub secrets, and pushes the image to the docker hub repository `myorg/myrepository`:
+
+```yaml
+uses: docker/build-push-action@v1
+with:
+  username: ${{ secrets.DOCKER_USERNAME }}
+  password: ${{ secrets.DOCKER_PASSWORD }}
+  repository: myorg/myrepository
+  tags: latest
+```
+
+The following will build the root Dockerfile, tag the image with the git reference and sha as described above, logs in to docker hub using GitHub secrets, and pushes the image to the docker hub repository `myorg/myrepository`:
+
+```yaml
+uses: docker/build-push-action@v1
+with:
+  username: ${{ secrets.DOCKER_USERNAME }}
+  password: ${{ secrets.DOCKER_PASSWORD }}
+  repository: myorg/myrepository
+  tag_with_ref: true
+  tag_with_sha: true
+```
+
+The following will only push the image when the event that kicked off the workflow was a push of a git tag:
+
+```yaml
+uses: docker/build-push-action@v1
+with:
+  username: ${{ secrets.DOCKER_USERNAME }}
+  password: ${{ secrets.DOCKER_PASSWORD }}
+  repository: myorg/myrepository
+  tag_with_ref: true
+  push: ${{ startsWith(github.ref, 'refs/tags/') }}
+```
+
+The following builds the `mytarget` stage and pushes that:
+ 
+```yaml
+uses: docker/build-push-action@v1
+with:
+  username: ${{ secrets.DOCKER_USERNAME }}
+  password: ${{ secrets.DOCKER_PASSWORD }}
+  repository: myorg/myrepository
+  tag_with_ref: true
+  target: mytarget
+```

action.yml

@@ -20,7 +20,7 @@ inputs:
     description: Docker repository to tag the image with
     required: true
   tags:
-    description: Comma-delimited list of tags. These will be added to the server/repository to form the image's tags
+    description: Comma-delimited list of tags. These will be added to the registry/repository to form the image's tags
     required: false
   tag_with_ref:
     description: Automatically tags the built image with the git reference as per the readme
@@ -48,7 +48,7 @@ inputs:
     description: Comma-delmited list of build-time variables
     required: false
   labels:
-    description: Comma-delimited list of labels to add to the built image. E.g. `label_name_1=label_value_1,label_name_2=label_value_2`
+    description: Comma-delimited list of labels to add to the built image
     required: false
   add_git_labels:
     description: Adds labels with git repo info to the built image