Here's a short overview of 3.0 source format support in git-buildpackage 0.4.64:
- git-import-dsc & git-import-dscs import 3.0 (quilt and native) format packages.
- git-import-orig: imports gzip and bz2 compressed archives. Other formats will be enabled once pristine-tar supports them (#499489).
- git-buildpackage handles creating gzip, bzip2, lzma and xz compressed tarballs with the --git-compression option although it could get a bit smarter and autodetect the compression type.
The newer kids in town gbp-clone, gbp-pull (for keeping the repo up to date when using team maintenance) and gbp-pq (for managing the quilt patch-queue) don't care about the underlying source package format. These three are a bit underdocumented in the manual but information about the workflow is in the wiki.