I have a large task ahead of me...modifying several hudson jobs' configuration. What I would want is to do it from command line. But per my experience, hudson will not re-read the configuration unless you force it to "reload configuration from disk".
I don't want to restart hudson just for a small change...like doing a "reload" in apache. Don't know how to read a java code but I'm guessing that what I am looking for lies in the part after saving configuration changes.
Hudson / Jenkins holds it's runtime configuration in memory, and only reloads it at startup or when you "reload configuration from disk".
However, reload configuration from disk is not a restart, just a re-read of the configuration.
That's all your choices, reload or restart.
Hacking it to work differently would be a major task, and if you can't yet read Java code, I wouldn't advise you to write it. Effectively you'd need to fork from the main project too, so updates won't be compatible.
If you need to do all the updates via a script, and then auto-reload the config, use hudson_cli.jar to do it.