Repository.create_reference only accepts str and not bytes

Repository.create_reference only accepts str and not bytes. This is because Repository_create_reference_direct in repository.c uses the s specifier for parsing that argument, which only accepts str and implicitly encodes it using UTF-8. I would expect it to accept str or bytes, and if you pass bytes, it uses exactly what you pass in with no encoding/decoding.

This is a similar problem to #932.

从 repository.c 中的 Repository_create_reference_direct 开始，检查 reference 参数是如何解析的。检查现有的 Repository.create_reference 行为以及相关的 issue #932，以确定预期的处理方式，然后验证 str 保持 UTF-8 编码，而 bytes 则原样传递。