Add "print-config" subcommand (#698)

* Add "show-config" subcommand

* Add integration tests

* Handle wrong additional args

* Support "BackupFilenameExpand" option

* Rename to print-config

* Remove config nil check as it will never be nil

* Rework print config to work with config.resolve()

* Use defer unset()

* Add warning about feature not being stable yet

test/print-config/conf.d/01print-config.env

@@ -0,0 +1,2 @@
+BACKUP_SOURCES=/conf-backup
+NOTIFICATION_URLS_FILE=/run/secrets/notification_urls

test/print-config/docker-compose.confd.yml

@@ -0,0 +1,6 @@
+services:
+  backup:
+    image: offen/docker-volume-backup:${TEST_VERSION:-canary}
+    volumes:
+      - ${CONF_DIR}:/etc/dockervolumebackup/conf.d:ro
+      - ${SECRET_FILE}:/run/secrets/notification_urls:ro

test/print-config/docker-compose.yml

@@ -0,0 +1,10 @@
+services:
+  backup:
+    image: offen/docker-volume-backup:${TEST_VERSION:-canary}
+    environment:
+      BACKUP_FILENAME: "backup-$${BACKUP_TAG}.tar"
+      BACKUP_FILENAME_EXPAND: true
+      BACKUP_TAG: expanded
+      BACKUP_SOURCES: /backup
+      NOTIFICATION_URLS: "stdout://"
+      AWS_S3_BUCKET_NAME: example-bucket

test/print-config/run.sh

@@ -0,0 +1,68 @@
+#!/bin/sh
+
+set -e
+
+cd "$(dirname "$0")"
+. ../util.sh
+current_test=$(basename $(pwd))
+
+info "print-config with environment variables"
+docker compose up -d --quiet-pull
+logs=$(docker compose exec -T backup backup print-config)
+
+echo "$logs"
+
+if ! echo "$logs" | grep -q "source=from environment"; then
+  fail "Missing source line."
+fi
+pass "Source line present."
+
+if ! echo "$logs" | grep -q "BackupSources:/backup"; then
+  fail "Missing BACKUP_SOURCES in output."
+fi
+pass "BACKUP_SOURCES present."
+
+if ! echo "$logs" | grep -q "BackupFilename:backup-expanded.tar"; then
+  fail "Missing expanded BACKUP_FILENAME in output."
+fi
+pass "Expanded BACKUP_FILENAME present."
+
+if ! echo "$logs" | grep -q "NotificationURLs:\[stdout://\]"; then
+  fail "Missing NOTIFICATION_URLS in output."
+fi
+pass "NOTIFICATION_URLS present."
+
+if ! echo "$logs" | grep -q "AwsS3BucketName:example-bucket"; then
+  fail "Missing AWS_S3_BUCKET_NAME in output."
+fi
+pass "AWS_S3_BUCKET_NAME present."
+
+docker compose down
+
+info "print-config with conf.d and _FILE"
+export CONF_DIR=$(pwd)/conf.d
+export SECRET_FILE=$(mktemp)
+printf "stdout://\n" > "$SECRET_FILE"
+
+docker compose -f docker-compose.confd.yml up -d --quiet-pull
+logs=$(docker compose -f docker-compose.confd.yml exec -T backup backup print-config)
+
+echo "$logs"
+
+if ! echo "$logs" | grep -q "source=01print-config.env"; then
+  fail "Missing conf.d source line."
+fi
+pass "conf.d source line present."
+
+if ! echo "$logs" | grep -q "BackupSources:/conf-backup"; then
+  fail "Missing conf.d BACKUP_SOURCES in output."
+fi
+pass "conf.d BACKUP_SOURCES present."
+
+if ! echo "$logs" | grep -q "NotificationURLs:\\[stdout://"; then
+  fail "Missing conf.d NOTIFICATION_URLS in output."
+fi
+pass "conf.d NOTIFICATION_URLS present."
+
+docker compose -f docker-compose.confd.yml down
+rm -f "$SECRET_FILE"