Can someone explain what this shell script does? (docker entrypoint in node-14 dockerfile)

Question

I'd like to understand what this script does. It's defined as the entrypoint for the node-14 docker-image. We have issues with our environment variables disappearing on this new version and I'm wondering if it has to do with this script (the env vars have some special characters in them). Could someone break it down for me?

#!/bin/sh
set -e

if [ "${1#-}" != "${1}" ] || [ -z "$(command -v "${1}")" ]; then
  set -- node "$@"
fi

exec "$@"

Answer 1

[ "${1#-}" != "${1}" ] -- "first parameter starts with a dash"

[ -z "$(command -v "${1}")" ] -- "cannot find a binary with a name set in the first parameter ${1}"

set -- node "$@" -- "insert 'node' at the first place in the parameters list"

exec "$@" -- "take all the parameters as a string and execute it"

Looks like this has nothing to do with environment variables.

P.S. I think in the second block of code (with "command") the inner double quotes should be escaped.