Comment by e40

Our main repo has git history back to 1985. RCS to CVS to git. Each step was lossless. I don’t remember the exact tool, but the CVS to git step was a fantastic Ruby program. It was incremental and each night I had a cron job that would update a checked out copy of the sources on the git side and diff with a copy from CVS. After 6 months I had confidence and the training of everyone was complete and we switched over.