Example common scenario: - Use stable firefox as your browser. - Build a firefox nightly with `mach build`. - Try to run it with `mach run`. Problem: - It doesn't run because "another instance of firefox is already running". This is confusing. Solutions: - `mach run -P dev` can help you, if you find out about it. - I think `mach run` should default to a profile that is different from the stable installation.
I don't think that's necessarily a good idea. I'm running this browser instance with mach run right nuw.
I like the idea of allowing the profile behavior to be what you proposed, but I don't think it makes sense for everyone, as Ms2ger has demonstrated. We /really/ need to come up with a better config file / settings story for mach. I don't think mozconfigs are the answer. That's something I'm going to try to hash out in the next month or two. If you want to implement this behind an environment variable in the interim, go for it.