add an option to only run the subcommand when files change #22
Description
Right now hupper runs the command immediately and then kills / restarts it when files change. Some interesting use-cases open up if it has an option to only run the command when files change. For example:
hupper --wait-for-changes -- docker restart app
If the command exits then hupper already will wait for files to change and run it again. I think this issue is just about not running it at startup.
This is likely contingent on changes in #19