git history-move

#!/bin/bash

print_usage () {
    echo "Usage: git history-move [-d] [-r file regex] <target-directory> [<rev-list options>]"
    echo
    echo "A helper script for \`git filter-branch\` for moving selected files to another directory in Git history."
    echo
    echo "positional arguments:"
    echo "  <target-directory>   The target directory the selected files will be moved to."
    echo "  <rev-list options>   Arguments for \`git rev-list\`. All positive refs included by these options are rewritten."
    echo "                       See \`man git-filter-branch\` for more details."

    echo
    echo "optional arguments:"
    echo "  -d   Dry run, only print files that would be moved."
    echo "  -r   Regex filter for files being moved, defaults to '.*' (matches every string)."
    echo "       Hint: By default the regex will match every substring of a given file path,"
    echo "             use '^{regex}$' to match the complete string instead."
}

parse_options () {
    DRY_RUN=0
    FILE_REGEX=".*"
    while getopts ":dr:" opt; do
        case ${opt} in
            d)
                DRY_RUN=1
                ;;
            r)
                FILE_REGEX="${OPTARG}"
                ;;
            :)
                >&2 echo "Option '-${OPTARG}' requires an argument."
                exit 1
                ;;
            \?)
                >&2 echo "Invalid option: '-${OPTARG}'"
                print_usage
                exit 1
                ;;
            *)
                print_usage
                exit 1
                ;;
        esac
    done
    shift $((OPTIND-1))
    TARGET_DIR="$1"
    if [[ "${TARGET_DIR}" == "" ]]; then
        >&2 echo "Please specify a target directory!"
        print_usage
        exit 1
    fi
    shift
    REMAINING_ARGS=( "$@" )
}

filter_git_repository () {
    local TMP_SCRIPT_DIR RETURN_CODE

    TMP_SCRIPT_DIR="$(mktemp -d)" || return 1
    cat <<- EOF > "${TMP_SCRIPT_DIR}/filter.sh"
		#!/bin/bash
		if (( ${DRY_RUN} )); then
		    echo
		fi
		git ls-tree --name-only "\${GIT_COMMIT}" | while read -r FILE; do
		    if [[ ! "\${FILE}" =~ ${FILE_REGEX} ]]; then
		        continue
		    fi
		    if (( ${DRY_RUN} )); then
		        echo " -> Would move \${FILE} to ${TARGET_DIR}/"
		    else
		        if [[ ! -d "${TARGET_DIR}" ]]; then
		            mkdir -p "${TARGET_DIR}"
		        fi
		        mv "\${FILE}" "${TARGET_DIR}/"
		    fi
		done
	EOF
    chmod +x "${TMP_SCRIPT_DIR}/filter.sh" && \
    git filter-branch --prune-empty --tree-filter "${TMP_SCRIPT_DIR}/filter.sh" "${REMAINING_ARGS[@]}"
    RETURN_CODE="$?"
    rm -rf "${TMP_SCRIPT_DIR}"
    return "${RETURN_CODE}"
}

main () {
    parse_options "$@" && \
    filter_git_repository
}

main "$@"