Errors for GetRef are inconsistent #1208
Description
When using GetRef the errors can be confusing. Because the error that is returned when a ref doesn't exist is not consistent.
If I want to check for existence of a specific branch feat/a, my repo contains the branch feat/alpha the GetRef call will return a specific error. If, however, my repo contains no branch for which feat/a is a prefix I get a error 404.
IMHO, it is better for the library to also special case where the ref doesn't exist and return the same error.