Submodule a branch on git

branch.git

$ git checkout -b [name_of_your_new_branch]
$ git push origin [name_of_your_new_branch]
$ git branch

$ git checkout master
$ git submodule add -b gh-pages git@github.com:blindgaenger/foobar.git _site
$ git status
# On branch master
# Changes to be committed:
#   (use "git reset HEAD <file>..." to unstage)
#
#    new file:   .gitmodules
#    new file:   _site
#
$ git commit -m "added gh-pages as submodule"
$ git push