Update doc with PAT for private repos

README.md

@@ -45,7 +45,7 @@ Optional Authentication: Create a Personal Access Token (PAT) for authentication
     - Note: `Read-only token for OSSF Scorecard Action - myorg/myrepo` (Note: replace `myorg/myrepo` with the names of your organization and repository so you can keep track of your tokens.)
     - Expiration: `No expiration`
     - Scopes: 
-        * `repo > public_repo`                  Required to read [Branch-Protection](https://github.com/ossf/scorecard/blob/main/docs/checks.md#branch-protection) settings.
+        * `repo > public_repo`                  Required to read [Branch-Protection](https://github.com/ossf/scorecard/blob/main/docs/checks.md#branch-protection) settings. Warning: for private repositories, you need scope `repo`.
         * `admin:org > read:org`                Optional: not used in current implementation.
         * `admin:repo_hook > read:repo_hook`    Optional: needed for the experimental [Webhook](https://github.com/ossf/scorecard/blob/main/docs/checks.md#webhooks) check.
         * `write:discussion > read:discussion`  Optional: not used in current implementation.
@@ -101,6 +101,8 @@ To verify that the Action is running successfully, click the repository's Action
 ### Troubleshooting 
 If the run has failed, the most likely reason is an authentication failure. Confirm that the Personal Access Token is saved as an encrypted secret within the same repository (see [Authentication](#authentication)). 
 
+If you install Scorecard on a private repository with a PAT token, provide the `repo:` scope. (The `repo > public_repo` scope only provides access to public repositories.)
+
 If you install Scorecard on a repository owned by an organization that uses [SAML SSO](https://docs.github.com/en/enterprise-cloud@latest/authentication/authenticating-with-saml-single-sign-on/about-authentication-with-saml-single-sign-on) or if you see `403 Resource protected by organization SAML enforcement` in the logs, be sure to [enable SSO](https://docs.github.com/en/enterprise-cloud@latest/authentication/authenticating-with-saml-single-sign-on/authorizing-a-personal-access-token-for-use-with-saml-single-sign-on) for your PAT token (see [Authentication](#authentication)).
 
 If the PAT is saved as an encrypted secret and the run is still failing, confirm that you have not made any changes to the workflow yaml file that affected the syntax. Review the [workflow example](#workflow-example) and reset to the default values if necessary.