ability to create separate branch per upstream release

(rephrased from the original, see the history button in gitlab)

For kali, it would be useful to have separate branches for each release. Perhaps a "dont_reuse_branch: true" setting in publish {} that can be set for some suites that provide a unique identifier (in the case of fresh-releases, a version number) for differentiating branches. This wouldn't apply to lintian-fixes.