Back when I forked Ikarus to begin Vicare development: I was not experienced in using Git and the tools available for repository conversion where not developed as they are today. The first commit I did was just a registration of the head of the trunk from Ikarus’ repository; I did not import the whole history of Ikarus development. I regret this.
Today it is easy to import such history from the original BZR repository into a Git repository, but grafting it to the beginning of Vicare’s history is another matter: IIUC doing it right implies rewriting the whole Vicare history. Uploading such big thing from my computer to a remote site, through my not–so–fast Internet connection, would be… adventurous.
I doubt that a viable solution will emerge.