docs: update backup file docs (#149)

* update backup file path

* docs: copy pasteable

* docs: add docstring returns

docs/how-to/resize-jenkins-storage.md

@@ -10,37 +10,43 @@ From [Backing-up/Restoring Jenkins](https://www.jenkins.io/doc/book/system-admin
 * Plugins (`.hpi` and `.jpi` files) in the `./plugins` folder
 
 ```bash
+echo cat <<EOF > backup.sh
 #!/bin/bash
 export JENKINS_HOME=/var/lib/jenkins
 export JENKINS_BACKUP=/mnt/backup
 
-echo "running backup as $(whoami) in $(pwd)"
-mkdir -p $JENKINS_BACKUP
-cp $JENKINS_HOME/secrets/master.key $JENKINS_BACKUP
-cp -r $JENKINS_HOME/*.xml $JENKINS_BACKUP
-cp -r $JENKINS_HOME/jobs $JENKINS_BACKUP
-cp -r $JENKINS_HOME/builds $JENKINS_BACKUP
-cp -r $JENKINS_HOME/workspace $JENKINS_BACKUP
-mkdir -p $JENKINS_BACKUP/plugins
-cp -r $JENKINS_HOME/plugins/*.hpi $JENKINS_BACKUP/plugins
-cp -r $JENKINS_HOME/plugins/*.jpi $JENKINS_BACKUP/plugins
+echo "running backup as \$(whoami) in \$(pwd)"
+mkdir -p \$JENKINS_BACKUP
+cp \$JENKINS_HOME/secrets/master.key \$JENKINS_BACKUP
+cp -r \$JENKINS_HOME/*.xml \$JENKINS_BACKUP
+cp -r \$JENKINS_HOME/jobs \$JENKINS_BACKUP
+cp -r \$JENKINS_HOME/builds \$JENKINS_BACKUP
+cp -r \$JENKINS_HOME/workspace \$JENKINS_BACKUP
+mkdir -p \$JENKINS_BACKUP/plugins
+cp -r \$JENKINS_HOME/plugins/*.hpi \$JENKINS_BACKUP/plugins
+cp -r \$JENKINS_HOME/plugins/*.jpi \$JENKINS_BACKUP/plugins
 
 chown -R 2000:2000 $JENKINS_BACKUP
 tar zcvf jenkins_backup.tar.gz --directory=/mnt backup
+EOF
+
+chmod +x backup.sh
 ```
 1. Transfer the backup script above to the running unit of the Jenkins-k8s charm and run it
 ```bash
-juju scp --container jenkins ./backup.sh jenkins-k8s/0:/backup.sh
-juju ssh  --container jenkins jenkins-k8s/0 /bin/bash
-bash /backup.sh
+JENKINS_UNIT=jenkins-k8s/0
+juju scp --container jenkins ./backup.sh $JENKINS_UNIT:/backup.sh
+juju ssh  --container jenkins $JENKINS_UNIT /backup.sh
 ```
 2. Retrieve the compressed backup file
 ```bash
-juju scp --container jenkins jenkins-k8s/0:/backup/jenkins_backup.tar.gz jenkins_backup.tar.gz
+JENKINS_UNIT=jenkins-k8s/0
+juju scp --container jenkins $JENKINS_UNIT:/jenkins_backup.tar.gz jenkins_backup.tar.gz
 ```
 3. With the data backed-up, we can remove the jenkins-k8s application.
 ```bash
-juju remove-application jenkins-k8s
+JENKINS_APP=jenkins-k8s
+juju remove-application $JENKINS_APP
 ```
 
 ## Restore the backup on a new charm instance
@@ -50,13 +56,14 @@ juju deploy jenkins-k8s --storage jenkins-home=10GB
 ```
 2. Wait for the charm to be ready, then restore the backup on the new unit.
 ```bash
-juju scp --container jenkins ./jenkins_backup.tar.gz jenkins-k8s/0:/jenkins_backup.tar.gz
-tar zxvf jenkins_backup.tar.gz
-chown -R 2000:2000 /backup
-cp -R /backup/* /var/lib/jenkins
-rm -rf /backup /jenkins_backup.tar.gz
+JENKINS_UNIT=jenkins-k8s/0
+juju scp --container jenkins ./jenkins_backup.tar.gz $JENKINS_UNIT:/jenkins_backup.tar.gz
+juju ssh --container jenkins $JENKINS_UNIT tar zxvf jenkins_backup.tar.gz
+juju ssh --container jenkins $JENKINS_UNIT chown -R 2000:2000 /backup
+juju ssh --container jenkins $JENKINS_UNIT cp -R /backup/* /var/lib/jenkins
+juju ssh --container jenkins $JENKINS_UNIT rm -rf /backup /jenkins_backup.tar.gz
 ```
 3. Finally restart pebble
 ```bash
-pebble restart jenkins
-```
+juju ssh --container jenkins $JENKINS_UNIT pebble restart jenkins
+```

tests/integration/test_plugins.py

@@ -355,10 +355,13 @@ async def test_thinbackup_plugin(ops_test: OpsTest, unit_web_client: UnitWebClie
     )
     res.raise_for_status()
 
-    async def has_backup():
+    async def has_backup() -> bool:
         """Get whether the backup is created.
 
         The backup folder of format FULL-<backup-date> should be created.
+
+        Returns:
+            Whether the backup file has successfully been created.
         """
         ret, stdout, stderr = await ops_test.juju(
             "ssh", "--container", "jenkins", unit_web_client.unit.name, "ls", backup_path