Checking out submodules. Put git submodule sync && git submodule update --init --recursive into `.git/hooks/post-checkout` and never again wonder why you

Checking out submodules. Put git submodule sync && git submodule update --init --recursive into `.git/hooks/post-checkout` and never again wonder why your code doesn't work after switching branches (because you forgot to update submodules). Also put it into `post-rewrite` so that the same works for `git rebase`.