bigtop-repos seems like an old, temp. hack which needs to be removed to avoid confusions. The only commit related to it is from BIGTOP-51, which was moving a bunch of stuff around. The only function this directory serves is to serve distributions file during apt creation. And even at this it's quite out-dated ie the version of the distribution is stuck at 0.1, etc.
I'd suggest we generate this dynamically as a part of the build, so the version is correct and we don't have a stale template.