I just pulled up Slicer github to look for something, and noticed all the stars were gone… ouch!
Perhaps this has already been hashed out in depth, but FWIW, throwing away a strong github profile is unfortunate and might be detrimental – users/contributors/granting organizations make a lot of decisions about project viability based on star count …for better or worse. As one example, I think github star count helped to qualify Slicer for free discourse hosting, even though we were somewhat below their listed minimum count.
I guess that a motivation for creating the repo from scratch was to maintain issue number continuity from mantis, but I would suggest transferring the issues from mantis in to a “github mantis archive” repo instead, which could then be cross-referenced (and the issue transfer seems to only be titles anyway…).
It may also be helpful to know that you can then you can move issues from the “github mantis archive” to the “real” Slicer repository as needed, maintaining a chain of history (github creates back and forward links), and avoiding the situation where someone will need to triage ~500 issues by going back to mantis (better to triage on-demand).
This would also avoid losing the pull-request history on the existing repo, which seems more valuable than title-only mantis issue numbers.
$.02 from the bleachers!