docs: make it clearer that most auth inputs are deprecated (#459)

Author: sethvargo

README.md

@@ -1,25 +1,11 @@
-<!--
- Copyright 2019 Google LLC
-
- Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
- compliance with the License. You may obtain a copy of the License at
-
-        https://www.apache.org/licenses/LICENSE-2.0
-
- Unless required by applicable law or agreed to in writing, software distributed under the License
- is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
- implied. See the License for the specific language governing permissions and limitations under the
- License.
--->
-
 # `setup-gcloud` GitHub Action
 
 Configures the [Google Cloud SDK][sdk] in the GitHub Actions environment. The Google Cloud SDK includes both the [gcloud][gcloud] and
 [gsutil][gsutil] binaries.
 
 Or integrate natively with other Google Cloud GitHub Actions:
 
-* [Authenticate to Google Cloud](https://github.com/google-github-actions/auth)
+* [Authenticate to Google Cloud][auth]
 * [Deploy a Cloud Run service](https://github.com/google-github-actions/deploy-cloudrun)
 * [Deploy an App Engine app](https://github.com/google-github-actions/deploy-appengine)
 * [Deploy a Cloud Function](https://github.com/google-github-actions/deploy-cloud-functions)
@@ -33,7 +19,7 @@ Or integrate natively with other Google Cloud GitHub Actions:
     rename the branch to `main` in 2022 and this _will break_ existing
     workflows. See [Versioning](#versioning) for more information.**
 
--   **Previously this repository contained the code for ALL of the GCP GithHub
+-   **Previously this repository contained the code for ALL of the GCP GitHub
     Actions. Now each action has it's own repo and this repo is only for
     `setup-gcloud`.**
 
@@ -81,18 +67,52 @@ jobs:
 
 ## Inputs
 
-| Name          | Requirement | Default | Description |
-| ------------- | ----------- | ------- | ----------- |
-| `version`     | _optional_  | `latest`| The version of the `gcloud` to be installed. Example: `290.0.1`|
-| `project_id`  | _optional_  | | ID of the Google Cloud Platform project. If provided, this will configure `gcloud` to use this project ID by default for commands. Individual commands can still override the project using the `--project` flag which takes precedence. |
-| `service_account_email` | _optional_  | | Service account email address to use for authentication. This is required for legacy .p12 keys but can be omitted for JSON keys. This is usually of the format `<name>@<project-id>.iam.gserviceaccount.com`. |
-| `export_default_credentials`| _optional_  |`false`| Exports the path to [Default Application Credentials][dac] as the environment variable `GOOGLE_APPLICATION_CREDENTIALS` to be available in later steps. Google Cloud services automatically use this environment variable to find credentials. |
-| `credentials_file_path`     | _optional_  | (temporary file) | Only valid when `export_default_credentials` is `true`. Sets the path at which the credentials should be written. |
-| `cleanup_credentials` | _optional_ | `true` | If true, the action will remove exported credentials from the filesystem upon completion. This only applies if `export_default_credentials` is true. |
-| `service_account_key`   | _optional_  | | (**Deprecated**) This input is deprecated. See [auth section](https://github.com/google-github-actions/setup-gcloud#authorization) for more details. The service account key which will be used for authentication credentials. This key should be [created](https://cloud.google.com/iam/docs/creating-managing-service-account-keys) and stored as a [secret](https://help.github.com/en/actions/automating-your-workflow-with-github-actions/creating-and-using-encrypted-secrets). It can be encoded as a [Base64](https://en.wikipedia.org/wiki/Base64) string or as JSON. |
+### Cloud SDK inputs
+
+-   `version`: (Optional) A string representing the version of the Cloud SDK
+    (`gcloud`) to install (e.g. `"290.0.1"`). The default value is "latest",
+    which will install the latest available Cloud SDK version.
+
+-   `project_id`: (Optional) Project ID (**not** project _number_) of the Google
+    Cloud project. If provided, this will configure the `gcloud` CLI to use that
+    project ID for commands. Individual commands can still override the project
+    with the `--project` flag. If unspecified, the action attempts to find the
+    "best" project ID by looking at other inputs and environment variables.
+
+### Authentication inputs
+
+**⚠️ Deprecated**: The following authentication inputs are deprecated and will
+be removed in a future release. See [Authorization](#authorization) for more
+information.
+
+-   `service_account_key`: (**Deprecated**, optional) The Google Cloud service
+    account key JSON. This key should be created and stored as a GitHub secret.
+    It can be the raw JSON contents or a base64-encoded string of the raw JSON
+    contents. There is no default value.
+
+-   `service_account_email`: (**Deprecated**, optional) Email address of the
+    service account to use for authentication. This is only required for p12
+    service account keys, which are no longer recommended. This input is not
+    required if using a JSON service account key. There is no default value.
+
+-   `export_default_credentials`: (**Deprecated**, optional) If true, the action
+    will write credentials to the filesystem and export the
+    `GOOGLE_APPLICATION_CREDENTIALS` environment variable for future steps to
+    consume [Application Default Credentials][adc]. The default value is false.
+
+-   `credentials_file_path`: (**Deprecated**, optional) The path at which the
+    exported credentials should be written on disk. In order for the credentials
+    to be available for future steps, it must be in `$GITHUB_WORKSPACE` or
+    `$RUNNER_TEMP`. This is only valid when `export_default_credentials` is
+    true. The default value is a temporary file inside `$GITHUB_WORKSPACE`.
+
+-   `cleanup_credentials`: (**Deprecated**, optional) If true, the action will
+    remove any generated credentials from the filesystem after all steps have
+    completed. This only applies if `export_default_credentials` is true. The
+    default value is true.
 
 
-## Example Workflows
+## Example workflows
 
 * [Google Kubernetes Engine](./example-workflows/gke/README.md): An example workflow that uses GitHub Actions to deploy a static website to an existing [Google Kubernetes Engine](https://cloud.google.com/kubernetes-engine/) cluster.
 
@@ -108,7 +128,9 @@ code to [App Engine](https://cloud.google.com/appengine), a fully managed server
 
 ## Authorization
 
-This action installs the Cloud SDK (`gcloud`). To configure its authentication to Google Cloud, use the [google-github-actions/auth](https://github.com/google-github-actions/auth) action. You can authenticate via:
+This action installs the Cloud SDK (`gcloud`). To configure its authentication
+to Google Cloud, use the [google-github-actions/auth][auth] action. You can
+authenticate via:
 
 ### Workload Identity Federation (preferred)
 
@@ -201,7 +223,8 @@ See [LICENSE](LICENSE).
 
 
 [github-action]:https://help.github.com/en/categories/automating-your-workflow-with-github-actions
-[dac]: https://cloud.google.com/docs/authentication/production
+[auth]: https://github.com/google-github-actions/auth
+[adc]: https://cloud.google.com/docs/authentication/production
 [sdk]: https://cloud.google.com/sdk/
 [gcloud]: https://cloud.google.com/sdk/gcloud/
 [gsutil]: https://cloud.google.com/storage/docs/gsutil