message: Make push optional
diff: #!/bin/bash
  set -e
  +if [[ "$1" == "-p" ]]; then
  + shift
  + push=1
  +else
  + push=0
  +fi
  +
  tag="neqoquic/neqo-qns:${1:-latest}"
  branch="${1:-main}"
  @@ -9,12 +16,16 @@ cd "$(dirname "$0")"
  rev=$(git log -n 1 --format='format:%H' -- .)
  [[ "$rev" != "$(cat .last-update)" ]] || (echo "No change since $rev."; exit 0)
  +# This makes the local .git directory the source, allowing for the current
  +# build to be build and pushed.
  [[ ! -e .git ]] || ! echo "Found .git directory. Script still active. Exiting."
  trap 'rm -rf .git' EXIT
  cp -R ../.git .git
  docker build -t "$tag" --build-arg NEQO_BRANCH="$branch" .
  +if [[ "$push" == "1" ]]; then
  docker login
  docker push "$tag"
  +fi
  echo "$rev" > .last-update
  