作曲家依赖关系的缓慢更新，尽管有 --prefer-dist 标志

为什么我的作曲家依赖项最多需要两分钟才能更新，即使没有更改也是如此？

一个流行的建议是附加标志：--prefer-dist

php composer.phar update --prefer-dist

但就我而言，这没有什么区别。下面是我的 composer.json 文件 – 我是否遗漏了一些明显的东西？

{
    "name": "my-namespace/symfony",
    "type": "project",
    "description": "",
    "require": {
        "php": ">=5.3.3",
        "symfony/symfony": "2.3.*",
        "doctrine/orm": ">=2.2.3,<2.4-dev",
        "doctrine/doctrine-bundle": "1.2.*",
        "twig/extensions": "1.0.*",
        "symfony/assetic-bundle": "2.3.*",
        "symfony/monolog-bundle": "2.3.*",
        "sensio/framework-extra-bundle": "2.3.*",
        "sensio/generator-bundle": "2.3.*",
        "sensio/distribution-bundle": "2.2.*",
        "my-namespace/my-bundle": "1.0.*"
    },
   "repositories": [
        {
            "type": "vcs",
            "url": "http://username:password@git.com/my-bundle.git"
        }
    ],    
    "scripts": {
        "post-install-cmd": [
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::buildBootstrap",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::clearCache",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::installAssets",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::installRequirementsFile"
        ],
        "post-update-cmd": [
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::buildBootstrap",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::clearCache",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::installAssets",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::installRequirementsFile"
        ]
    },
    "config": {
        "bin-dir": "bin"
    },
    "minimum-stability": "dev",
    "extra": {
        "symfony-app-dir": "app",
        "symfony-web-dir": "web",
        "branch-alias": {
            "dev-master": "2.3-dev"
        }
    }
}