pointer to the looked-up reference
the repository to look up the reference
the long name for the reference (e.g. HEAD, refs/heads/master, refs/tags/v0.1.0, ...)
0 on success, git_error_code.GIT_ENOTFOUND, git_error_code.GIT_EINVALIDSPEC or an error code.
Lookup a reference by name in a repository.
The returned reference must be freed by the user.
The name will be checked for validity. See git_reference_symbolic_create() for rules about valid names.