We would like to have the ability to pass a .sif file to the wrapper so it uses it for execution

[jmtcsngr]

Currently the singularity-*-docker wrapper scripts produced when installing, will pull the image from docker or rely on the singluarity cache. But it should be possible to use a .sif file saved locally to execute.

So instead of using
singularity exec/run "docker://$DOCKER_REGISTRY/$DOCKER_USER/$DOCKER_IMAGE:$DOCKER_TAG" "$@"

We would like to be able to do ask the wrapper to do
singularity exec/run "${CONTAINER}" "$@"
where $CONTAINER is either a docker://... or a <path to local .sif file> and the behaviour is controlled by the calling wrapper executable. Essentially define where to find the image at run time when executing write_wrapper
.