Add prefer-stable:true to dev packages

[tristanlins]

No description provided.

[discordier]

@tristanlins could you please(!) write more explicit tickets?
I mean having a thought and putting it in a ticket is ok, but fill it with a little flesh later.

Now I have to guess which dev packages you mean. Those of our client or those of the installation (root composer.json) or which ones?
As this is only to be interpreted in the root json, I wonder what you are thinking of here.

[tristanlins]

We are talking about the composer dist generator - see the repository name ;-) - there are only 2 packages/environments that are for dev:
https://github.com/ContaoCommunityAlliance/composer-dist/tree/master/dev-phar
https://github.com/ContaoCommunityAlliance/composer-dist/tree/master/dev (will be removed, see #2)
And there is only one composer.json in this package/environment?!

I wonder you are wondering about this :D

[discordier]

aaaaaaaaah, sry. Missed the repo name. XD
Nevermind.