Release arg in ubuntu-device-flash

[Sergio Schvezov]

On Mon, Jun 08, 2015 at 04:45:44PM +0200, Martin Pitt wrote:
> Hey all,
> 
> Federico Gimenez [2015-06-08 16:36 +0200]:
> > Hello all, while reviewing the snappy guides I've found in several places
> > references to u-d-f's release argument. However, the u-d-f man page doesn't
> > mention it (version 0.20-0ubuntu1) and if you call the command without it
> > gives this error:
> > 
> > $ sudo ubuntu-device-flash --verbose core --output=/tmp/snappy.img
> > --developer-mode
> > the required argument `Release` was not provided
> 
> I don't understand why this new argument is necessary. To me, release
> and channel are not independent concepts; a channel has pre-built
> images which are based on a particular Ubuntu release (that we
> choose). So from what I understand, someone calling u-d-f can't have
> any freedom wrt. to which release to pick, this should be all implied
> by the channel name.
> 
> There is no implied default for this new mysterious "release"
> argument, and if we provide it in autopkgtest's "snappy" ssh setup
> script then it will stop working on 15.04 and earlier where u-d-f does
> not yet expect this.
> 
> So, my questions:
> 
>  * Why is this necessary at all?

Because we are moving to the new concept for channels, per snappy
package and driven by the store. The system image channels which were
both a channel and a release are going away.

>  * How can a program find out the correct release for a given channel?

I don't understand this question, but snappy cares for the release, not
the channel for finding packages on the store. Packaging has no encoding
for the release.

>  * What's the recommended way to find out whether or not u-d-f needs
>    this argument? Is there anything easier than parsing --help output?

This is a required argument and I regret ever adding a manpage.