Can’t get composer “path” repository to work

I posted the issue on Github as well and it turns out that the documentation is a little misleading. It says:

{
    "repositories": [
        {
            "type": "path",
            "url": "../../packages/my-package"
        }
    ],
    "require": {
        "my/package": "*"
    }
}

However, if you just have a local repo without releases, you have to use:

{
    "repositories": [
        {
            "type": "path",
            "url": "../../packages/my-package"
        }
    ],
    "require": {
        "my/package": "dev-master"
    }
}

The version dev-master is the key here (given that you are working on the master branch). This was mildly infuriating, but thanks to some helpful composer contributors, I could finally get a grip on this.