checkout-submodules

#!/bin/bash -e

usage() {
    echo "Usage: $0 [<ref>]"
    echo
    echo "Make the submodules in a repository match the given ref (e.g. a commit, branch, or tag)."
    exit 1
}

ref="$1"
if [ -z "$ref" ]; then ref="master"; fi
sha="$(git rev-parse $ref)" || usage

echo "Checking out submodules for $ref ($sha)"
git submodule foreach "(git -C \$toplevel checkout $sha \$path && git -C \$toplevel add \$path) || exit 0"
echo "Done."
git status
echo "Changes for preceeding submodules are staged, run 'git commit' to commit."