Given an on-disk file that contains the raw content of an object, determine the object ID. This prepends the object header to the given data, and hashes the results with the hash corresponding to the given oid_type.

Note that this does not look at attributes or do any on-disk filtering (like line ending translation), so when used with blobs, it may not match the results for adding to the repository. To compute the object ID for a blob with filters, use git_repository_hashfile.