Have you tried comparing the existing orig tarball from the archive tothe corresponding tarball downloaded via uscan?
$ curl -sSL 'http://http.debian.net/debian/pool/main/libr/librabbitmq/librabbitmq_0.5.0.orig.tar.gz'
| sha1sum
826286c3f04695bdc231d8e7b0541f871975cdcc -
$ curl -sSL 'https://github.com/alanxz/rabbitmq-c/archive/v0.5.0.tar.gz'
| sha1sum
826286c3f04695bdc231d8e7b0541f871975cdcc -
Also, looking in Git, it would appear that Michael is currently working
on packaging 0.5.1. ;)