Add label to optionally skip container restart after backup (#659)

* Add label to optionally skip container restart after backup

* Add new mutually exclusive label instead

* Simplified `hasLabel`

* removed unnecessary else block

* added new test-case `no-restart` based on test-case `local`

* removed invalid README entry

* added new section to how-tos

* Added configuration reference

test/no-restart/docker-compose.yml

@@ -0,0 +1,27 @@
+services:
+  backup:
+    image: offen/docker-volume-backup:${TEST_VERSION:-canary}
+    hostname: hostnametoken
+    restart: always
+    environment:
+      BACKUP_FILENAME_EXPAND: 'true'
+      BACKUP_FILENAME: test-$$HOSTNAME.tar.gz
+      BACKUP_LATEST_SYMLINK: test-$$HOSTNAME.latest.tar.gz.gpg
+      BACKUP_CRON_EXPRESSION: 0 0 5 31 2 ?
+      BACKUP_RETENTION_DAYS: ${BACKUP_RETENTION_DAYS:-7}
+      BACKUP_PRUNING_LEEWAY: 5s
+      BACKUP_PRUNING_PREFIX: test
+    volumes:
+      - app_data:/backup/app_data:ro
+      - /var/run/docker.sock:/var/run/docker.sock:ro
+      - ${LOCAL_DIR:-./local}:/archive
+
+  offen:
+    image: offen/offen:latest
+    labels:
+      - docker-volume-backup.stop-during-backup-no-restart=true
+    volumes:
+      - app_data:/var/opt/offen
+
+volumes:
+  app_data:

test/no-restart/run.sh

@@ -0,0 +1,76 @@
+#!/bin/sh
+
+set -e
+
+cd "$(dirname "$0")"
+. ../util.sh
+current_test=$(basename $(pwd))
+
+export LOCAL_DIR=$(mktemp -d)
+
+docker compose up -d --quiet-pull
+sleep 5
+
+# A symlink for a known file in the volume is created so the test can check
+# whether symlinks are preserved on backup.
+docker compose exec offen ln -s /var/opt/offen/offen.db /var/opt/offen/db.link
+docker compose exec backup backup
+
+sleep 5
+
+expect_running_containers "1"
+
+tmp_dir=$(mktemp -d)
+tar -xvf "$LOCAL_DIR/test-hostnametoken.tar.gz" -C $tmp_dir
+if [ ! -f "$tmp_dir/backup/app_data/offen.db" ]; then
+  fail "Could not find expected file in untared archive."
+fi
+rm -f "$LOCAL_DIR/test-hostnametoken.tar.gz"
+
+if [ ! -L "$tmp_dir/backup/app_data/db.link" ]; then
+  fail "Could not find expected symlink in untared archive."
+fi
+
+pass "Found relevant files in decrypted and untared local backup."
+
+if [ ! -L "$LOCAL_DIR/test-hostnametoken.latest.tar.gz.gpg" ]; then
+  fail "Could not find symlink to latest version."
+fi
+
+pass "Found symlink to latest version in local backup."
+
+# The second part of this test checks if backups get deleted when the retention
+# is set to 0 days (which it should not as it would mean all backups get deleted)
+BACKUP_RETENTION_DAYS="0" docker compose up -d
+sleep 5
+
+docker compose exec backup backup
+
+if [ "$(find "$LOCAL_DIR" -type f | wc -l)" != "1" ]; then
+  fail "Backups should not have been deleted, instead seen: "$(find "$local_dir" -type f)""
+fi
+pass "Local backups have not been deleted."
+
+# The third part of this test checks if old backups get deleted when the retention
+# is set to 7 days (which it should)
+
+BACKUP_RETENTION_DAYS="7" docker compose up -d
+sleep 5
+
+info "Create first backup with no prune"
+docker compose exec backup backup
+
+touch -r "$LOCAL_DIR/test-hostnametoken.tar.gz" -d "14 days ago" "$LOCAL_DIR/test-hostnametoken-old.tar.gz"
+
+info "Create second backup and prune"
+docker compose exec backup backup
+
+if [ -f "$LOCAL_DIR/test-hostnametoken-old.tar.gz" ]; then
+  fail "Backdated file has not been deleted."
+fi
+
+if [ ! -f "$LOCAL_DIR/test-hostnametoken.tar.gz" ]; then
+  fail "Recent file has been deleted."
+fi
+
+pass "Old remote backup has been pruned, new one is still present."