split directories into branches

I've got a chef cookbook repo where everyone started developing cookbooks in a single dev branch (not project specific). Minus a few edge cases, it should be fairly simple to split this up into feature branches based on /cookbooks/<feature>.

I tried: $ git filter-branch --subdirectory-filter cookbooks/<feature>-- <feature> And $ git subtree split --prefix cookbooks/<feature> -b <feature>

Which both seem to do the same thing (haven't looked at the subtree bash - guessing it does exactly the filter-branch). The issue is that it removes the directory tree (so obviously merges wouldn't work). I'm thinking some type of filter-branch --index-filter with a cherry pick (or similar) should work...?