Restore files that were backed up by Syncthing as "sync conflicts"

restoresyncthing.sh

#!/bin/bash --posix

# ------------------------------------------------------------------------
# Copyright (C) 2023  Atrate
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as
# published by the Free Software Foundation, either version 3 of the
# License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.
# ------------------------------------------------------------------------

# --------------
# Version: 0.1.0
# --------------

# ------------------------------------------------------------------------------
# Simple script that restores files marked as "sync conflict" by syncthing based
# on the timestamp (in days only)
# ------------------
# Exit code listing:
#   0: All good
#   1: Unspecified
#   2: Error in environment configuration or arguments
# ------------------------------------------------------------------------------


# Print script usage
# ------------------
print_usage()
{
    cat << USAGE >&2
Usage:  $(basename "$0"): [OPTIONS] TIMESTAMP
Recursively restore files in the current working directory from a Syncthing
sync-conflict backup.

Options:
  -h, --help        print this usage information
  -n, --dry-run     show what would be done, don't perform any other actions

Examples:
    $(basename "$0") 20230902

The TIMESTAMP argument needs to be in the format YYYYMMDD.
USAGE
    return 0
}


# Parse commandline options
# Adapted from https://stackoverflow.com/a/29754866
# -------------------------------------------------
parse_options()
{
    # Check whether getopt version is "enhanced"
    # shellcheck disable=SC2251
    # ------------------------------------------
    ! getopt --test >&3
    if [[ ${PIPESTATUS[0]} -ne 4 ]]
    then
        err 'This script requres getopt enhanced to work properly'
        exit 2
    fi

    # Set available options
    # ---------------------
    LONGOPTS=dry-run,help
    # LONGOPTS+=,config:
    OPTIONS=hn
    # OPTIONS+=c:

    # Get arguments from "$@" using getopt
    # ------------------------------------
    IFS=" " read -r -a PARSED <<< "$(getopt --options=$OPTIONS --longoptions=$LONGOPTS --name "$0" -- "$@")"
    eval set -- "${PARSED[*]}"

    # Declare argument variables' default values
    # ------------------------------------------
    declare -g DRYRUN="false"

    # Write to argument variables
    # ---------------------------
    while true
    do
        case "$1" in
            -h|--help)
                print_usage
                exit 0
                ;;
            -n|--dry-run)
                DRYRUN="true"
                shift
                ;;
            --)
                shift
                break
                ;;
            *)
                echo "Invalid argument"
                print_usage
                exit 2
                ;;
        esac
    done

    # Handle positional arguments ($1, $2, …)
    # ---------------------------------------
    if [[ $# -ne 1 ]]
    then
        echo "$(basename "$0"): TIMESTAMP required but not provided"
        print_usage
        exit 2
    else
        # Check whether $1 is a correct TIMESTAMP
        # ---------------------------------------
        if echo "$1" | grep -qE '^[0-9]{8}$'
        then
            declare -g TIMESTAMP
            TIMESTAMP=$1
        else
            echo "$(basename "$0"): TIMESTAMP needs to be in the format YYYYMMDD"
            exit 2
        fi
    fi

    return
}


# Main program functionality
# --------------------------
main()
{
    while read -r file
    do
        # Skip empty lines/empty input
        # ----------------------------
        [ -z "$file" ] && continue

        # Extract the original filename
        # -----------------------------
        local target
        target="$(echo "$file" \
                  | sed -E "s/\.sync-conflict-$TIMESTAMP-[0-9]*-[0-9A-Z]*//")"

        if [ "$DRYRUN" = "true" ]
        then
            # Echo what would be done
            # -----------------------
            echo cp -vaf -- "$file" "$target"
        else
            # Copy the backed-up file over the 'original'
            # -------------------------------------------
            cp -vaf -- "$file" "$target"
        fi

    done <<< "$(find . -type f -iname "*sync-conflict-$TIMESTAMP*")"
}

parse_options "$@"
main "$@"

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