How do I revert an unversioned file?

[Eli Zaretskii]

> From: Eric Siegerman <lists08-bzr at davor.org>
> Date: Thu, 13 Jan 2011 05:06:17 -0500
> 
> On Thu, 2011-01-13 at 04:00 -0500, Glenn Morris wrote:
> > Contents conflict in path/to/file
> > bzr revert path/to/file
> > bzr: ERROR: Path(s) are not versioned: path/to/file
> 
> Try "bzr revert path/to/file.OTHER".  Strange but true...

Could you say a few words about how this works and why?

TIA