Converting from svn to git: another reason not to use external references
Usually it is easy to import a subversion repository into git. You just do this:
mkdir my_project cd my_project git svn init svn://repo.url/goes/here git svn fetch
This will always fetch the repository you specified, but sometimes in svn your project actually depends on multiple repositories (ie: you use external references). The external reference will not be fetched and you will have to manually add it in somehow.
Did you really think it would be that easy?