Function write_ref 

pub fn write_ref(git_dir: &Path, refname: &str, oid: &ObjectId) -> Result<()>

Write a ref, creating parent directories as needed.

Dispatches to the reftable backend when extensions.refStorage = reftable.

Parameters

• git_dir — path to the git directory.
• refname — reference name (e.g. "refs/heads/main").
• oid — the new target object ID.

Errors

Returns Error::Io on filesystem errors.