Clients today expect the repo to clean up if there are unused blobs, not to
manually delete things they think are unused. Let's do that, and use
umoci's code to do it since it's tested and works.
v2: also run GC on update as well as delete
v3: fix up error return paths needing two args
Signed-off-by: Serge Hallyn <shallyn@cisco.com>
Signed-off-by: Tycho Andersen <tycho@tycho.ws>
Fixes issue #67.
As per dist spec, DELETE of a image manifest can only be done with
digest as <reference> param. Previously, tags were being allowed as
well. This is not conformant to the spec.
