gitlab-ci: Dynamic artifact names

I am running a gitlab-ci job that will fetch locally a file from a remote server, more or less as follows:

retrieve_docs:
    stage: fetch_docs
    image: debian:jessie
    script:
      - ssh $USERNAME@$SERVER /perform/some/work
      - INSTFILE=$(ssh $USERNAME@$SERVER bash -c 'find /root -iname "somepattern*" | tail -n 1 | xargs readlink -f')
      - echo "Will retrieve locally $INSTFILE"
      - scp $USERNAME@$SERVER:$INSTFILE .
      - BASEFILE=$(basename $INSTFILE)
      - mv $BASEFILE downloads/
    artifacts:
      name: $BASEFILE
      paths:
        - downloads/

The above job definition however does not seem to work, as the BASEFILE variable is rendered as empty when providing the filename.

• Is there a way to use dynamic artifact name(s)?

• Is there a reason that this artifact is also never copied in my (empty/tracked) downloads folder?

• The above process will actually fetch a .zip file locally. Is there a way (although I have set expiration of 1 week) to have each job delete old artifacts and keep only the latest artifact / zip file?