refuse to upgrade pre-v3 packages

[pharext/pharext] / composer.json

{
        "name": "m6w6/pharext",
        "description": "Package PHP extensions as self-installing PHARs",
        "keywords": ["ext", "extension", "phar", "package", "install"],
        "type": "project",
        "license": "BSD-2-Clause",
        "bin": [
                "bin/pharext", 
                "bin/pharext.pubkey",
                "bin/pharext.update",
                "bin/pharext.update.key"
        ]
}