Describe the bug
After updating Backrest to 1.13.0, checking an SFTP repository fails because the generated restic command appears to pass an invalid --option=sftp.args=... value. I wanted to adapt a hook, but now cannot save it.

Backrest reports:

invalid argument "sftp.args=-oBatchMode=yes -i \"/root/.ssh/id_ed25519_backrest_hetzner\" -p 23 -oUserKnownHostsFile=\"/root/.ssh/known_hosts\"" for "-o, --option" flag: parse error on line 1, column 30: bare " in non-quoted-field

The generated flag seems to be:

--option=sftp.args='-oBatchMode=yes -i "/root/.ssh/id_ed25519_backrest_hetzner" -p 23 -oUserKnownHostsFile="/root/.ssh/known_hosts"'

To Reproduce
Steps to reproduce the behavior:

1. Update Backrest to 1.13.0

2. Configure an SFTP repository using custom SFTP args, including quoted paths, for example:

   -oBatchMode=yes -i "/root/.ssh/id_ed25519_backrest_hetzner" -p 23 -oUserKnownHostsFile="/root/.ssh/known_hosts"

3. Run a repository check

4. See the error shown in the screenshot

Expected behavior
The repository check should run successfully, or Backrest should generate/pass the sftp.args option in a format accepted by restic.

Screenshots

Platform Info

• OS and Architecture: Linux / Docker on Raspberry Pi 5 arm64
• Backrest Version: 1.13.0

Additional context
This started after updating to Backrest 1.13.0. The issue seems related to quoting/escaping in the generated --option=sftp.args=... argument.

Luckily backups still work fine with the saved config, but I cannot modify it now.