Direct reftable repository creation fails to set the repository format, storage and structure #307

Version

all versions, including master.

Operating System

Linux/Unix

Bug description

FileRepository creation.

When the selected ref backend is a FileReftableDatabase, create() wrote core.repositoryformatversion=0 and never persisted extensions.refStorage=reftable.

A freshly opened repository therefore selected RefDirectory, disagreeing with the on-disk reftable storage.
create() also skipped the backward-compatibility layout (refs/, a dummy HEAD, the refs/heads blocker), so FileKey detection did not recognize the repository.

Actual behavior

FileRepository creates an inconsistent representation of a extensions.refStorage repository on disk.

Expected behavior

FileRepository creates a correct repository with a extensions.refStorage repository on disk.

Relevant log output

Other information

No response