Option to default to no-dev? (Willing to provide PR)

[yakatz]

I want to see if this is acceptable before I spend time on a PR:

I would like a way on my servers to make composer default to not installing require-dev pacakges. It seems like the simplest way to do this would be to add a COMPOSER_NO_DEV environment variable, and allow specifying --with-dev to override it.
I see that the --dev command line option is marked as deprecated and will be removed in Composer 3, however, I didn't find any discussion of this change, so I apologize if this has been previously discussed.

As I said, I would be happy to write up a PR, but I was wondering if there is any more background information.

[Seldaek]

I think adding a COMPOSER_NO_DEV sounds reasonable, but I'm not sure if I'd add a --with-dev flag or just say if you set the env you can make sure to invoke with COMPOSER_NO_DEV=0 to cancel it. I suspect places where the env is set would never really need to do with dev? If you have a mixed use case then passing --no-dev when needed is fine. That'd keep the change to a smaller scope. WDYT?

[yakatz]

Sounds good. I finally had a chance to put together a patch (#10262), but I am having some issues figuring out the tests.