Detach subdirectory into separate Git repository and preserve history (see http://stackoverflow.com/q/359424/802365)

extract-to-submodule.bash

#!/usr/bin/env bash
# DESCRIPTION:
#   Detach subdirectory into separate Git repository and preserve history (see http://stackoverflow.com/q/359424/802365)
#
# USAGE:
#   bash -x ./extract-to-submodule.bash password-strength password-toggle phone-ribbon


if [[ $# -lt 2 ]]; then
    echo "missing parent directory or subdirectories list."
    exit;
else
    fat_repo="$(pwd)/$1"; shift 1
    ancestor_dir="$fat_repo/.."
    subdirs=( "$@" )
    echo "Extracting ${subdirs[@]}."
fi

for subdir in "${subdirs[@]}"; do
    cd "$fat_repo"/
    module="ui-$subdir"
    module_remote="ssh://[email protected]:33622/akema-lab/$module.git"

    # isolate to branch
    git subtree split --prefix="$subdir" --branch="$subdir"

    # extract to new directory
    mkdir "$ancestor_dir/$module" \
        && cd "$ancestor_dir/$module" \
        && git init \
        && git pull "$fat_repo" "$subdir" \
        && git remote add origin "$module_remote" \
        && git push origin -u master

    # clean fat repo
    cd "$fat_repo"/
    git rm -rf "$subdir"
    git submodule add "$module_remote" "$module"
done