Do not skip directories when creating tar archive (#72)

* Update targz library to include potential ownership fix

* Move archive logic to main repo

* Remove assertions for debugging

* Use relative path in assertion

* Strip local part from archive location

* Log when extracting in tests

* Fix trimming of prfix

* Add license info to archive.go file

* Undo change in test assertion

* Add test checking for preserved file ownership

* use same postgres version in tests

* Wrap errors when archiving, handle deletion at script layer

test/ownership/run.sh

@@ -0,0 +1,28 @@
+#!/bin/sh
+# This test refers to https://github.com/offen/docker-volume-backup/issues/71
+
+set -e
+
+cd $(dirname $0)
+
+mkdir -p local
+
+docker-compose up -d
+sleep 5
+
+docker-compose exec backup backup
+
+sudo tar --same-owner -xvf ./local/backup.tar.gz -C /tmp
+
+sudo find /tmp/backup/postgres > /dev/null
+echo "[TEST:PASS] Backup contains files at expected location"
+
+for file in $(sudo find /tmp/backup/postgres); do
+  if [ "$(sudo stat -c '%u:%g' $file)" != "70:70" ]; then
+    echo "[TEST:FAIL] Unexpected file ownership for $file: $(sudo stat -c '%u:%g' $file)"
+    exit 1
+  fi
+done
+echo "[TEST:PASS] All files and directories in backup preserved their ownership."
+
+docker-compose down --volumes