Add support for SHA256 repositories

New input parameter 'repo-sha256' to set the Git object format
to "sha256" when initializing a Git repository.

action.yml

@@ -98,6 +98,10 @@ inputs:
   github-server-url:
     description: The base URL for the GitHub instance that you are trying to clone from, will use environment defaults to fetch from the same instance that the workflow is running from unless specified. Example URLs are https://github.com or https://my-ghes-server.example.com
     required: false
+  repo-sha256:
+    description: 'Set Git object format to "sha256" when initializing a Git repository.'
+    required: false
+    default: false
 outputs:
   ref:
     description: 'The branch, tag or SHA that was checked out'