Indeed, we went [something old] -> FogBugz -> Jira and cvs -> svn -> git. All cases from that original system have been lost and some but not all of the FogBugz cases were imported to Jira (and even the ones that were imported are hard to find), while the repos went through an import process so all commits and their messages have been preserved. The git history is a bit wonky because of how branches work differently, but "blame", check commit, "blame commit~1" to iterate backwards in the history to track a change do all still work as expected.

We now have been having to stop devs from using Gitlab as their primary issue tracker instead of Jira because the non-devs use Jira for everything and we need to keep them in the loop.