Clarification between migrate and mirror about imap-backup HOT 4 CLOSED

@grigarr Sorry for the lack of response on this.

I agree that the functionality offered by imap-backup is hard to understand.

While thinking about, I realised that neither of the existing commands are quite right.

• migrate copies messages, but doesn't avoid duplicates when re-run,
• mirror copies messages, avoiding duplicates, but wants to delete any messages it doesn't recognise (via the .mirror file)

I've decided to replace both with the copy command. migrate and mirror will be soft deprecated from the next release, and deleted in the future (unless there is a reason to keep one/both).

copy tracks what it copies and avoids duplicate copies. It ignores whatever else is in the destination folder as it's the user's job to decide whether they want a clean 'mirror' from account to account or some kind of merge where messages arrive from other sources.

I've pushed the branch and will be testing it before merging and releasing.

from imap-backup.