Initial implementation.

Makefile

@@ -0,0 +1,9 @@
+PLUGINS := tarback/*.sh
+SCRIPT  := tarback.sh
+PREFIX  ?= /usr/local
+
+install: $(PLUGINS)
+	install -D -t $(PREFIX)/share/tarback -m 0644 -o root -g root $^
+	install -D -m 0755 -o root -g root $(SCRIPT) $(PREFIX)/bin/
+
+.PHONY: install

tarback.sh

@@ -0,0 +1,121 @@
+#!/bin/sh
+
+set -e
+
+XDG_DATA_HOME="${XDG_DATA_HOME:-$HOME/.local/share}"
+XDG_DATA_DIRS="${XDG_DATA_DIRS:-/usr/local/share:/usr/share}"
+
+# example: TARBACK_REMOTE="ssh myuser@myserver" ./tarback ...
+TARBACK_REMOTE="${TARBACK_REMOTE:-}"
+# maybe the command needs to be transformed before being passed to the
+# remote command, see _transform_ssh_command for an example
+TARBACK_TRANSFORM_REMOTE_COMMAND="${TARBACK_TRANSFORM_REMOTE_COMMAND:-}"
+# shellcheck disable=SC2016 # disable variable not expanding hint
+[ -z "$TARBACK_TAR_CREATE_COMMAND" ] \
+    && TARBACK_TAR_CREATE_COMMAND='tar c -C "$(dirname "$1")" "$(basename "$1")"'
+# shellcheck disable=SC2016 # disable variable not expanding hint
+[ -z "$TARBACK_TAR_EXTRACT_COMMAND" ] \
+    && TARBACK_TAR_EXTRACT_COMMAND='tar x -C "$(dirname "$1")"'
+[ -z "$TARBACK_COMPRESSION" ] && TARBACK_COMPRESSION="xz"
+[ -z "$TARBACK_SPLIT" ] && TARBACK_SPLIT="split -b $((128*1024*1024)) -"
+[ -z "$TARBACK_MERGE" ] && TARBACK_MERGE='cat'
+[ -z "$TARBACK_PLUGIN_SEARCH_PATH" ] \
+    && TARBACK_PLUGIN_SEARCH_PATH="$(dirname "$0"):$XDG_DATA_HOME:$XDG_DATA_DIRS"
+
+TARBACK_PLUGIN_SEARCH_PATH="$(echo "$TARBACK_PLUGIN_SEARCH_PATH" | tr ':'  '\n')"
+
+_transform_split_name() {
+    command_name="$(echo "$TARBACK_SPLIT" | awk '{print $1}')"
+    if echo "$command_name" | grep -q 'split'; then
+        echo "$1.part"
+    else
+        echo "$1"
+    fi
+}
+
+_transform_ssh_command() {
+    command_name="$(echo "$TARBACK_REMOTE" | awk '{print $1}')"
+    if echo "$command_name" | grep -q 'ssh'; then
+        echo "'$1'"
+    else
+        echo "$1"
+    fi
+}
+
+_transform_remote() {
+    r="$1"
+    # TODO add more transformers
+    for t in _transform_ssh_command "$TARBACK_TRANSFORM_REMOTE_COMMAND"; do
+        [ -z "$t" ] && continue # skip empty transformers
+        r="$("$t" "$r")"
+    done
+    echo "$r"
+}
+
+create() {
+    # $1 ... src
+    # $2 ... dst
+    src="$1"
+    dst="$(_transform_split_name "$2")"
+    tarback_tar_create_command="$(_transform_remote "$TARBACK_TAR_CREATE_COMMAND")"
+    $TARBACK_REMOTE sh -c "$tarback_tar_create_command" - "$src" \
+        | $TARBACK_COMPRESSION \
+        | $TARBACK_SPLIT "$dst"
+}
+
+restore() {
+    src="$(_transform_split_name "$1")"
+    dst="$2"
+    tarback_tar_extract_command="$(_transform_remote "$TARBACK_TAR_EXTRACT_COMMAND")"
+    $TARBACK_MERGE "$src"* \
+        | $TARBACK_COMPRESSION --decompress --stdout \
+        | $TARBACK_REMOTE sh -c "$tarback_tar_extract_command" - "$dst"
+}
+
+short_options='p:'
+while getopts "$short_options" arg; do
+    case "$arg" in
+        p)
+            # source plugin file
+            # shellcheck disable=SC1090 # disable cannot follow source
+            sourced=false
+            for loc in $TARBACK_PLUGIN_SEARCH_PATH; do
+                if [ -e "$loc/tarback/$OPTARG.sh" ]; then
+                    . "$loc/tarback/$OPTARG.sh"
+                    sourced=true
+                    break
+                fi
+            done
+            if ! "$sourced"; then
+                echo "couldn't find plugin $OPTARG" >&2
+                exit 1
+            fi
+            shift 2
+            ;;
+        *)
+            echo "unknown option $1" >&2
+            exit 1
+            ;;
+    esac
+done
+
+case "$1" in
+    create)
+        shift
+        if [ "$#" -eq 2 ]; then
+            create "$@"
+        else
+            echo 'not enough arguments, expected 2: src dest' >&2
+            exit 1
+        fi
+        ;;
+    restore)
+        shift
+        if [ "$#" -eq 2 ]; then
+            restore "$@"
+        else
+            echo 'not enough arguments, expected 2: src dest' >&2
+            exit 1
+        fi
+        ;;
+esac

tarback/docker.sh

@@ -0,0 +1,4 @@
+#!/bin/sh
+
+TARBACK_TAR_CREATE_COMMAND='docker run -i --rm --workdir=/mnt --volume="$1":/mnt/"$1" alpine '"$TARBACK_TAR_CREATE_COMMAND"
+TARBACK_TAR_EXTRACT_COMMAND='docker run -i --rm --workdir=/mnt --volume="$1":/mnt/"$1" alpine '"$TARBACK_TAR_EXTRACT_COMMAND"