Comment 2 for bug 1680574

On Thu, Apr 06, 2017 at 07:26:46PM -0000, Barry Warsaw wrote:
> $ ubuntu-image -w /tmp/wd pc-amd64.assertion
> $ ls /tmp/wd/root/system-data/var/lib/snapd/snaps/
> core_1636.snap pc-kernel_60.snap

> So that seems like the information you're asking for. I guess a file
> listing of that directory would be the manifest you want, right?

That would suffice. It might be nice to do some basic transformations here,
to make the manifest tabular - à la
<http://cdimage.ubuntu.com/ubuntu-base/daily/current/zesty-base-amd64.manifest>.

> Should we just add a -m/--manifest argument which names a file into which
> we would write these snap file names?

I think I would prefer it be written by default to the output dir under a
fixed name (and if not using -O, to write it out as <foo>.manifest alongside
<foo>.img). It's a cheap enough thing to create, and common enough to want,
that I think we should just do it as the sensible default thing instead of
requiring the user to ask for it. If they don't want it, it's a pretty
cheap file to clean up.