add_git_labels adds opencontainers labels

Setting the INPUT_ADD_GIT_LABELS env var to true adds labels as per the
opencontainers standard: https://github.com/opencontainers/image-spec/blob/master/annotations.md

The 3 labels supported are:
- org.opencontainers.image.created
- org.opencontainers.image.source
- org.opencontainers.image.revision

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

README.md

@@ -124,14 +124,15 @@ labels: label_name_1=label_value_1,label_name_2=label_value_2
 
 Boolean value. Defaults to `false`.
 
-Adds labels with git repository information to the built image.
+Adds labels with git repository information to the built image based on the standards set out in https://github.com/opencontainers/image-spec/blob/master/annotations.md.
 
 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.|
+|`org.opencontainers.image.created`|`2020-03-06T23:00:00Z`|Date and time on which the image was built (string, date-time as defined by RFC 3339).|
+|`org.opencontainers.image.source`|`https://github.com/myorg/myrepository`|URL to this repository.|
+|`org.opencontainers.image.revision`|`676cae2f85471aeff6776463c72881ebd902dcf9`|The full git sha of this commit.|
 
 
 ### `push`

action.yml

@@ -3,7 +3,7 @@ description: Builds and pushes Docker images and will log in to a Docker registr
 author: Docker
 runs:
   using: docker
-  image: docker://docker/github-actions:v0.0.1
+  image: docker://docker/github-actions:v0.1
   args:
     - build-push
 inputs:
@@ -51,7 +51,7 @@ inputs:
     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
+    description: Adds labels with git repository information to the built image
     required: false
     default: false
   push: