revset: store full detail into revsetalias.error for error source distinction Before this patch, any errors in the declaration of revset alias aren't detected at all, and there is no information about error source in the error message. As a part of preparation for parsing alias declarations and definitions more strictly, this patch stores full detail into "revsetalias.error" for error source distinction. This makes raising "Abort" and warning potential errors just use "revsetalias.error" without any message composing.