gitslave
Coordinated multi-repository super-projects for Git
... newbranch will create the new branch in all repositories.
Gitslave has been used for mid-sized product development with many slave repositories (representing different programs and plugins), branches, tags, and developers; and for single-person repositories tracking groups of .emacs and .vim repositories (in the latter case, it is basically used to keep the slave repositories up to date via a single command).