Don't error out if chown fails and avoid manually escaping quotes

[Guiorgy]

chown may fail when the destination file system doesn't support Unix ownership attributes. Since the success of chown isn't critical, if this happens, just print a warning and continue.

Fixes #37

Demo:

• Before this PR:

  $ sudo vackup export diun_data diun_data.tar.gz
  diun_data
  ./
  ./diun.db
  chown: /mount-volume/diun_data.tar.gz: Operation not permitted
  Error: Failed to start busybox backup container
  $ ls
  diun_data.tar.gz

• After this PR:

  $ sudo vackup export diun_data diun_data.tar.gz
  diun_data
  ./
  ./diun.db
  chown: /mount-volume/diun_data.tar.gz: Operation not permitted
  Warning: Failed to change ownership of the diun_data.tar.gz file
  Successfully tar'ed volume diun_data into file diun_data.tar.gz
  $ ls
  diun_data.tar.gz

Edit: Added 2nd commit, which passes variables to the Docker container as environmental variables and expands them inside the container. This avoids manually escaping quotes, which may fail if the file name contains a single/double quote character.

[Copilot]

Pull request overview

Updates vackup export to treat chown failures as non-fatal so exports succeed on filesystems that don’t support Unix ownership attributes (e.g., exFAT), aligning behavior with issue #37.

Changes:

• Wrap chown during export so a failure prints a warning and does not fail the overall export.
• Preserve export success message and exit code even when ownership change can’t be applied.

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[Guiorgy]

Linter failed on Dockerfile, in other words, unrelated to the PR.

[BretFisher]

Thanks, and sorry I sat on this for so long.

[Guiorgy]

Thanks, and sorry I sat on this for so long.

Nah, no worries at all, I've been using my own modified copy, the whole point of FOSS 😋