We just switched from Perforce to git at work, and about the first 2/3 of a project I work on got squashed together. It took me less than a week to bump in to that "initial commit" when trying to figure out why a bit of code is the way it is.
"git blame" (or the p4 equivalent) is my usual archaeologic tool in this context, but "git bisect" has been very helpful in others. For the first, it should be easy to look at your current codebase in SVN and see how far back the history goes in any particular area. I've found that bisection is most useful for relatively recent history, because I usually have wanted to build or run the software to test for a bug or something - beyond some point in history that becomes impractical.
Moving from SVN to git shouldn't require losing history though...
"git blame" (or the p4 equivalent) is my usual archaeologic tool in this context, but "git bisect" has been very helpful in others. For the first, it should be easy to look at your current codebase in SVN and see how far back the history goes in any particular area. I've found that bisection is most useful for relatively recent history, because I usually have wanted to build or run the software to test for a bug or something - beyond some point in history that becomes impractical.
Moving from SVN to git shouldn't require losing history though...