*
* On success, returns 0 and a pointer to the new, allocated dentry is stored in
* *dentry_ret. On failure, returns WIMLIB_ERR_NOMEM or an error code resulting
*
* On success, returns 0 and a pointer to the new, allocated dentry is stored in
* *dentry_ret. On failure, returns WIMLIB_ERR_NOMEM or an error code resulting