Servers configured with this [1] don't work, with [2] do work when importing repositories:
Error: Uncaught Exception: [RuntimeException] Failed to execute git clone --mirror 'https://git.tuxed.net/php-yubitwee.git' '/home/composer/.composer/cache/vcs/https---git.tuxed.net-php-yubitwee.git/' Cloning into bare repository '/home/composer/.composer/cache/vcs/https---git.tuxed.net-php-yubitwee.git'... fatal: unable to access 'https://git.tuxed.net/php-yubitwee.git/': gnutls_handshake() failed: Handshake failed