Import the git-repocache scripts
Import git-disconnect-alternates
Add a new git-repocache command for submodules
Add a new front-end function for updating submodules
Import git-env and git-tenv
Import git-scrub
Teach git-env and git-tenv about --recursive
Teach git-repocache-submodule to also run git-disconnect-alternates
Delete git-scrub because it can just be an alias
Delete git-su because it can just be an alias
Add basic front-end documentation to the Readme.