How to use a local version of a Docker image for testing a workflow?

For testing and debugging workflows quickly locally one could imagine that it would be useful to not have to pull a remote Docker image but be able to use a local one (example: Trying to test how changes to a Docker image affect a workflow). How do you tell packtivity to not pull an image, so that the local version is used?

This can be done by simply setting the environment variable PACKTIVITY_DOCKER_NOPULL (as of packtivity v0.8.3+ — the most recent version of recast-atlas (v0.1.9) requires packtivity>=0.14.23 for the local backend, so this will definitely work for you).

Example:

export PACKTIVITY_DOCKER_NOPULL=TRUE

recast run my-workflow --backend docker --tag local-image-debug