this command line interface is deprecated

I'm confused about this one.

With rdiff-backup-2.2.5 installed, I get the following warning "WARNING: this command line interface is deprecated and 
will disappear, start using the new one as described with '--new --help'."


https://rdiff-backup.net/FAQ.html says:

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30. Why does rdiff-backup complain about command line interface being deprecated even though I’m using the new syntax?

Calling for example rdiff-backup backup loc1 server2::loc2 leads to a message WARNING: this command line interface is 
deprecated and will disappear, start using the new one as described with '--new --help'.

You must be using a remote location in your call, as in our example. In order to make sure that the other side 
understands the call, rdiff-backup uses the CLI form fitting the default API version. For example, at time of writing, 
rdiff-backup 2.2 uses API 200 by default and hence calls rdiff-backup --server so that the CLI can be understood by 
rdiff-backup 2.0. If the server side is v2.2+, then the warning message will appear.

Call rdiff-backup with the higher API and the message will disappear.

Calling for example rdiff-backup --api-version 201 backup loc1 server2::loc2 will make sure that rdiff-backup server is 
being called, getting rid of the warning message.
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https://rdiff-backup.net/rdiff-backup.1.html says:

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--api-version apiversion

     Sets the API version to the given integer between minimum and maximum versions as given by the info action. It is 
the responsibility of the user to make sure that this version is also supported by any server started by this client.
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and

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regress [COMPRESSION OPTIONS] [USER GROUP OPTIONS] [TIMESTAMP OPTIONS] repository

     If an rdiff-backup session fails, this action will undo the failed directory. This happens automatically if you 
attempt to back-up to a directory and the last backup failed. You can use the --force option to undo the last backup 
even if it wasn’t failed (starting with API 201, use --api-version if necessary).
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What api is it talking about?
I  tried adding "--api-version 201" to the command, but that just errored out.

Wayne Sallee
[email protected]
http://www.WayneSallee.com