[OE-core] No versioning for existing images

[Laszlo Papp]

On Tue, Feb 25, 2014 at 7:22 AM, Anders Darander <anders at chargestorm.se> wrote:
> Well, if you set it as a variable, you can always use it in e.g. the
> IMAGE_PREPROCESS_COMMAND, to store it to a suitable file in the image.
> Just as I'm storing the output from git describe.

This makes me think that it would be nice to have a dedicated variable
for this version that automatically populates a "standard place", e.g.
/etc/version. That could standardize this process across projects,
although it could be made customizable on top of the default if one
wishes to do it differently. So, how about an IMAGE_VERSION variable
which would be put into the image name if specified, and the string
would also be put into some place on the target, like "/etc/version"?

> If you plan on keeping multiple image versions (which you should do at
> least for released images), you likely should then append your version
> number to the image names (and possibly some more info), or at least
> store them in a versioned tree/repository for easy retrieval.

Yes, I agree that version numbers should be put into the image name.
Yes, a "versioned tree" makes sense, which I think we can call a
mirror for instance. I think that is enough for binaries, and perhaps
it is better than a separate versioned repository on top of the
already existing tags.