This is the tool used to convert KDE's Subversion into multiple Git repositories. You can find more description and usage examples at https://techbase.kde.org/Projects/MoveToGit/UsingSvn2Git
Run qmake && make. You get ./svn-all-fast-export.
You need to write a rules file that describes how to slice the Subversion history into Git repositories and branches. See https://techbase.kde.org/Projects/MoveToGit/UsingSvn2Git.