juju should warn when "create-backup" is executed without --keep-copy

[Felipe Reyes]

In juju 2.4 there was a change in the behavior of "juju create-backup" (see https://bugs.launchpad.net/juju/+bug/1749300 ), users have been experiencing this change as a bug, because there is no message to let them know that create-backup doesn't keep the backup in the controller by default any more.

When someone executes create-backup without --download nor --keep-copy juju should print a message informing about this new behavior.

[Anastasia (anastasia-macmood)]

Fascinatingly scary, the users can also specify

$ juju create-backup --keep-copy=false --no-download

This will mean that we'll run this expensive process but nothing will be its result as the backup will not be downloaded nor stored on the controller :D

Interestingly, the command also provides verbose mode whereby the backup content will actually be printed as an output on stdout. I do wonder how useful this particular feature is... I would have expected that average backups are not small...

[Anastasia (anastasia-macmood)]

Verbose output only provides details about backup archive, metadata, and, consequently, is very useful.

Also, providing --keep-copy in combination is intriguing...

When specifying '--no-download' or '--no-download=true', '--keep-copy' will be hardcoded to 'true' to store that archive remotely. So, if user provides a value for -keep-copy, it will be ignored.

Specifying '--no-download=false' whilst possible, is also redundant, as this is the default behavior of the command. Essentially, it means "download the backup archive to my client'.

I am updating command help and clearer outputs as per suggestion in the description above.

[Anastasia (anastasia-macmood)]

PR against 2.4: https://github.com/juju/juju/pull/9052

[Anastasia (anastasia-macmood)]

PR against develop: https://github.com/juju/juju/pull/9053

[Felipe Reyes (freyes)]

Anastasia, thanks for quickly fixing this bug, much appreciated.