Merge branch 'master' into patch-2

README.md

@@ -17,6 +17,7 @@ Suggestions and issues can be posted on the repositories [issues page](https://g
 * [target](#target)
 * [always_pull](#always_pull)
 * [build_args](#build_args)
+* [cache_froms](#cache_froms)
 * [labels](#labels)
 * [add_git_labels](#add_git_labels)
 * [push](#push)
@@ -114,6 +115,15 @@ Example:
 build_args: arg1=value1,arg2=value2
 ```
 
+### `cache_froms`
+
+Comma-delimited list of images to consider as cache sources.
+
+Example:
+```yaml
+cache_froms: myorg/baseimage:latest
+```
+
 ### `labels`
 
 Comma-delimited list of labels to add to the built image.
@@ -194,6 +204,18 @@ with:
   target: mytarget
 ```
 
+The following will build the root Dockerfile, tag the image as `myorg/myrepository:latest`, log in to Google Container Registry using GitHub secrets (where `DOCKER_PASSWORD` is a [JSON key](https://cloud.google.com/container-registry/docs/advanced-authentication#json-key)), and push the image to the GCR repository `myorg/myrepository`:
+ 
+```yaml
+uses: docker/build-push-action@v1
+with:
+  username: _json_key
+  password: ${{ secrets.DOCKER_PASSWORD }}
+  registry: gcr.io
+  repository: myorg/myrepository
+  tags: latest
+```
+
 ### Minimal complete working github actions yaml file
 
 This minimal workflow clones the repo in question with the `actions/checkout@v1` step, and then runs `docker build -t myorg/myrepository .` with the `Dockerfile` present in the parent directory. In this case, it only builds it and does not push it (`push: false`). This can be useful for testing if the `Dockerfile` is valid in the first place and making sure there are no version conflicts.

action.yml

@@ -50,6 +50,9 @@ inputs:
   build_args:
     description: Comma-delimited list of build-time variables
     required: false
+  cache_froms:
+    description: Comma-delimited list of images to consider as cache sources
+    required: false
   labels:
     description: Comma-delimited list of labels to add to the built image
     required: false