containers-add on an existing (but not saved yet) image does not save it (annex add)

[yarikoptic]

datalad-container 1.1.5

invocation was

      datalad containers-add "$familyname" \
                    -i "$imagefile" \
                    --update \
                    --call-fmt '{img_dspath}/scripts/singularity_cmd run {img} {cmd}'

should check first (if not url is given, imagefile already there) if known to git, if not git annex add it first (save would create commit but I think ideally there should be a single commit adding container image to annex and then entry to config)