How to use the bloom.git.get_root function in bloom

def check_for_multiple_remotes():
    if get_root() is None:
        return
    remotes = get_remotes()
    if len(remotes) < 0:
        error("Current git repository has no remotes. "
              "If you are running bloom-release, please change directories.",
              exit=True)
    if len(remotes) > 1:
        error("Current git repository has multiple remotes. "
              "If you are running bloom-release, please change directories.",
              exit=True)

debug("_set_trim_sub_dir(" + str(sub_dir) + ", " + str(force) + ", " +
          str(config) + ", " + str(directory) + ")")
    if sub_dir is not None:
        if config['trim'] != '' and config['trim'] != sub_dir:
            warning("You are trying to set the trim sub directory to " +
                    sub_dir + ", but it is already set to " +
                    config['trim'] + ".")
            if not force:
                warning("Changing the sud directory is not advised. "
                        "If you are sure you want to do this, use "
                        "'--force'")
                return None
            else:
                warning("Forcing the change of the sub directory.")
        # Make the sub_dir absolute
        git_root = get_root(directory)
        sub_dir_abs = os.path.join(git_root, sub_dir)
        # Make sure it is a directory
        if not os.path.isdir(sub_dir_abs):
            error("The given sub directory, (" + sub_dir + ") does not "
                  "exist in the git repository at " + git_root)
            return None
        # Set the trim sub directory
        config['trim'] = sub_dir
    return config

def get_upstream_meta(upstream_dir, ros_distro):
    meta = None
    directory = os.getcwd()
    with change_directory(upstream_dir):
        if get_root() is not None:  # If in a git repo
            current_branch = get_current_branch()
        else:
            current_branch = None
        name, version, packages = get_package_data(current_branch, quiet=False, release_directory=directory)
    meta = {
        'name': name,
        'version': version,
        'type': 'package.xml'
    }
    return meta

if get_root() is None:
        # Not a git repository
        return
    track_branches(['bloom', BLOOM_CONFIG_BRANCH])
    if show('bloom', PLACEHOLDER_FILE) is not None:
        return
    if show('bloom', 'bloom.conf') is not None:
        # Wait for the bloom.conf upconvert...
        return
    if not branch_exists('bloom'):
        return
    _has_checked_bloom_branch = True
    info("Moving configurations from deprecated 'bloom' branch "
         "to the '{0}' branch.".format(BLOOM_CONFIG_BRANCH))
    tmp_dir = mkdtemp()
    git_root = get_root()
    try:
        # Copy the new upstream source into the temporary directory
        with inbranch('bloom'):
            ignores = ('.git', '.gitignore', '.svn', '.hgignore', '.hg', 'CVS')
            configs = os.path.join(tmp_dir, 'configs')
            my_copytree(git_root, configs, ignores)
            if [x for x in os.listdir(os.getcwd()) if x not in ignores]:
                execute_command('git rm -rf ./*')
            with open(PLACEHOLDER_FILE, 'w') as f:
                f.write("""\
This branch ('bloom') has been deprecated in favor of storing settings and overlay files in the master branch.

Please goto the master branch for anything which referenced the bloom branch.

You can delete this branch at your convenience.
""")

def upconvert_bloom_to_config_branch():
    global _has_checked_bloom_branch
    if _has_checked_bloom_branch:
        return
    # Assert that this repository does not have multiple remotes
    check_for_multiple_remotes()
    if get_root() is None:
        # Not a git repository
        return
    track_branches(['bloom', BLOOM_CONFIG_BRANCH])
    if show('bloom', PLACEHOLDER_FILE) is not None:
        return
    if show('bloom', 'bloom.conf') is not None:
        # Wait for the bloom.conf upconvert...
        return
    if not branch_exists('bloom'):
        return
    _has_checked_bloom_branch = True
    info("Moving configurations from deprecated 'bloom' branch "
         "to the '{0}' branch.".format(BLOOM_CONFIG_BRANCH))
    tmp_dir = mkdtemp()
    git_root = get_root()
    try:

def non_git_rebase(upstream_branch, directory=None):
    # Create a temporary storage directory
    tmp_dir = mkdtemp()
    # Get the root of the git repository
    git_root = get_root(directory)
    try:
        # Copy the new upstream source into the temporary directory
        with inbranch(upstream_branch):
            ignores = ('.git', '.gitignore', '.svn', '.hgignore', '.hg', 'CVS')
            parent_source = os.path.join(tmp_dir, 'parent_source')
            my_copytree(git_root, parent_source, ignores)
        # Clear out any untracked files
        execute_command('git clean -fdx', cwd=directory)  # for good measure?
        # Collect files (excluding .git)
        items = []
        for item in os.listdir(git_root):
            if item in ['.git', '..', '.']:
                continue
            items.append(item)
        # Remove all files
        if len(items) > 0:

if config['trimbase'] != '':
        warning("It looks like the trim operation has already been done, "
                "nested trimming is not supported.")
        if force:
            warning("Proceeding anyways because of '--force'")
        else:
            warning("If you would like to continue anyways use '--force'")
            return None
    current_branch = get_current_branch(directory)
    if current_branch is None:
        error("Could not determine current branch.", exit=True)
    config['trimbase'] = get_commit_hash(current_branch)
    tmp_dir = tempfile.mkdtemp()
    try:
        # Buckup trim sub directory
        git_root = get_root()
        sub_dir = os.path.join(git_root, config['trim'])
        storage = os.path.join(tmp_dir, config['trim'])
        shutil.copytree(sub_dir, storage)
        # Clear out any untracked files
        execute_command('git clean -fdx', cwd=directory)
        # Collect al files (excluding .git)
        items = []
        for item in os.listdir(git_root):
            if item in ['.git', '..', '.']:
                continue
            items.append(item)
        # Remove and .* files missed by 'git rm -rf *'
        if len(items) > 0:
            execute_command('git rm -rf ' + ' '.join(["'{}'".format(i) for i in items if i]), cwd=directory)
        # Copy the sub directory back
        for item in os.listdir(storage):