This is a Docker image for the text editor nano.
Get a FILE from a running CONTAINER to edit it:
docker cp CONTAINER:FILE /tmp/
docker run --name=nano -it --rm -v /tmp:/tmp piegsaj/nano nano /tmp/FILE
and put it back:
cat /tmp/FILE | docker exec -i CONTAINER sh -c 'cat > FILE'
rm /tmp/FILE
The source is available on Github. Please report any issues.