During the refactoring of the git module, I found there were some
strange operations. This PR tries to fix 2 of them
1. The empty argument `--` in repo_attribute.go, which was introduced by
#16773. It seems unnecessary because nothing else would be added later.
2. The complex git service logic in repo/http.go.
* Before: the `hasAccess` only allow `service == "upload-pack" ||
service == "receive-pack"`
* After: unrelated code is removed. No need to call ToTrustedCmdArgs
anymore.
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>