git-sub-ff-and-commit

#! /bin/bash

# Commit submodule at origin's master
#
# Grab master if it's at our current commit, skip to origin's master, commit a
# changelog to parent repo.
#
# To apply to all submodules, you can use:
#   git submodule foreach "cd - ; echo git sub-ff-and-commit \$name $*"

f() {
    module=$1
    remote=origin
    branch=master
    if [ $# -ge 3 ] ; then
        remote=$2
        branch=$3
    fi

    git -C $module use-branch-if-already-there $branch &&
        git -C $module fetch &&
        git -C $module merge --ff-only $remote/$branch &&
        git sub-commit-changelog $module
}

f $*