Release arg in ubuntu-device-flash

[Martin Pitt]

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?

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

 * 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?

Thank you in advance!

Martin
-- 
Martin Pitt                        | http://www.piware.de
Ubuntu Developer (www.ubuntu.com)  | Debian Developer  (www.debian.org)