Error inconsistencies

[akamensky]

There are too many errors for "Not found".

In my code to just be able to check if something is "not found" I have to do:

func IsNotFound(err error) bool {
	switch {
	case errors.Is(err, git.ErrBranchNotFound):
		return true
	case errors.Is(err, object.ErrDirectoryNotFound):
		return true
	case errors.Is(err, object.ErrEntryNotFound):
		return true
	case errors.Is(err, object.ErrFileNotFound):
		return true
	case errors.Is(err, object.ErrParentNotFound):
		return true
	case errors.Is(err, plumbing.ErrReferenceNotFound):
		return true
	case errors.Is(err, plumbing.ErrObjectNotFound):
		return true
	default:
		return false
	}
}

Now I stumbled on the fact that if I do clone over http, I get plumbing.ErrReferenceNotFound which is an error type and can be used with errors.Is().

But if i clone over ssh, i get git.NoMatchingRefSpecError, which is NOT an error type (it is a struct that implements error). For this one I have to add case git.NoMatchingRefSpecError{}.Is(err): return true to make it work.