So, I created a new repository (Mercurial) and wanted to add a Yii application to it by doing the composer dance but Yii 2 yelled at me because the directory wasn’t empty?
Could you stop that behavior, please? 
I know what I’m doing. 
I thought about creating a ticket for it at Github, but I am not sure where to put it.
There are literally nearly 1000 open tickets, so I thought I’d check here first.
It’s not Yii 2, it’s Composer. Put it in https://github.com/composer/composer/issues but it was discussed several times before.
D’oh.
And when I thought I had a just cause…
It’s not a big deal, so I guess I’d take a look at the Composer issue tracker.
It looks like it’s because of the way that Composer depends on Git:
Personally, I really hate the way that composer sometimes can pollute my vendor directory with Git stuff…
Of course, that is not a problem if the package maintainers have done a proper job.
Try adding –prefer-dist to your commands.
I usually do that, of course, but sometimes I use packages that does not exist in a stable (tagged) version