Git subtree splitter

git-split.sh

#!/bin/sh
#
# Git subtree splitter.
#
# Copyright (c) 2014-2015, Tilman Blumenbach
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
#
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in
#    the documentation and/or other materials provided with the
#    distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
# COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.

if [ $# -lt 2 ]; then
    echo "Usage:"
    echo " $0 export-dir subtree..."
    echo
    echo "This exports all named subtrees as separate git repositories"
    echo "to export-dir. Each repository directory under export-dir has"
    echo "the same name as the corresponding subtree."
    echo
    echo "This command needs to be executed in a git repository."

    exit 1
fi

export_dir=$1
shift

set -e
for subtree; do
    dest_dir=${export_dir}/${subtree}
    echo "Exporting '${subtree}' to '${dest_dir}'..."

    if [ ! -d "${subtree}" ]; then
        echo "Error: '${subtree}' does not exist. Skipping."
        continue
    fi

    # Else we can proceed.
    # 1. Create the destination directory.
    mkdir -p "${dest_dir}"

    # 2. Now, we can split the subtree:
    subtree_branch="exported_subtree_${subtree}__$(uuidgen)"
    git subtree split -q -b "${subtree_branch}" -P "${subtree}" >/dev/null

    # 3. Clone only the subtree.
    cd "${dest_dir}"
    git clone -q "${OLDPWD}" -b "${subtree_branch}" .

    # 4. Clean up the repository: Create a new master branch and delete the origin remote.
    git remote remove origin
    git checkout -q -b master
    git branch -q -d "${subtree_branch}"

    # 5. Finally, remove the temporary subtree branch in the source repository.
    cd - >/dev/null
    git branch -q -D "${subtree_branch}"
done