We started seeing a situation where buildbot would always use the master branch for distgit tasks regardless of which branch the package was built for.

We are indeed sending a branch param to buildbot but it turns out that there's a quirk in buildbot that overrides this value with ''. Buildbot merges change and build properties and apparently, the build params override the change params. The branch param of the build is '' and since that overrides the change build param (which we set @ trigger time), the build param is always '' by the time a build is run.

Find a way to fix this - it's causing problems for the modularity folks