Utterly irrelevant. A partial checkout won't make git noticeably faster, as it is pretty darn fast already. Believe me. A truncated history might save you up to 150MB, also totally not worth the effort, especially because then your custom git repo has different hashes and fetching/merging other peoples branches becomes impossible.

Furthermore, the point with git is to have multiple branches in your workspace and switch between them (again, this is frigging fast). I was juggling 8-10 branches at one time and have never had the need to create a second workspace ('git stash' being the keyword here).

Please have a look at http://wiki.freebsd.org/GitWorkflow and try it out!