ask user to add local sync folder if missing (instead of error)

[moscicki]

Use case: a user restored a previous version of the system from time machine backup (OSX). He does not have the sync folder enabled in the time machine (logically). After the restore the local sync folder was missing and the client reported "Unable to find local sync folder".

A possible improvement for the sync client would be to ask user if he wants the missing folder to be re-created automatically on startup of the client.

[dragotin]

You mean by restoring all data from the server? Nice convenience feature.

[SamuAlfageme]

I also believe this is the natural approach to go, instead of having to manually recreate the folder sync connection, allow the client to do that based on the mapping (which remote folder goes in which local one) still stored in the config file.

For comparison sake, this is what Dropbox (on Linux) asks when he's unable to locate the sync folder:

It offers the chance to manually put the folder there again (and do nothing then) or restore the whole thing from the server (Relinkoption).

[ckamm]

Relates to #5317 - an alternative cause of sync folders disappearing is because they are on removable storage, such as USB drives. If we do something here, we should keep that case in mind.