In November 2012 I helped the giant JBoss Tools repo containing 400+ eclipse plugins, 2+ millions line of code with 7+ year of history migrate from SVN into a multitude of Git repositories.
Most existing large migrations I could find info about was about the size as one of our 30+ modules in JBoss tools and it turned out the advice in most of these just did not cope with a migration as large as this.
During this tale I cover what tools I examined, rejected and in the end selected to do the migration. I will outline the migration process we did as a team, what things Git enabled immediately and which things we are moving towards now that Git have opened up for a more flexible build and development model and structure.
Before this move a 6+ months long preparation and even longer thinking process was started to ensure all data would be migrated properly in an efficient and repeatable manner with as little possible impact on developer productivity as possible.
After this talk you should be well prepared to do both small and large migrations to git for Eclipse based plugin projects and know what dangers to look out for and what tools to consider.
If you want to take a sneakpeak you can see the scripts and instructions for the migration at https://github.com/maxandersen/jbosstools-gitmigration