使用 brew 安装稳定版的 composer 版本是 1.2.0 的，可是一运行 composer 就提示：

PHP Fatal error:  Uncaught PharException: phar "/Users/wwx/Developer/Cellar/composer/1.2.0/libexec/composer.phar" SHA1 signature could not be verified: broken signature in /Users/wwx/Developer/Cellar/composer/1.2.0/libexec/composer.phar:23
Stack trace:
#0 /Users/wwx/Developer/Cellar/composer/1.2.0/libexec/composer.phar(23): Phar::mapPhar('composer.phar')
#1 {main}
  thrown in /Users/wwx/Developer/Cellar/composer/1.2.0/libexec/composer.phar on line 23

Fatal error: Uncaught PharException: phar "/Users/wwx/Developer/Cellar/composer/1.2.0/libexec/composer.phar" SHA1 signature could not be verified: broken signature in /Users/wwx/Developer/Cellar/composer/1.2.0/libexec/composer.phar on line 23

PharException: phar "/Users/wwx/Developer/Cellar/composer/1.2.0/libexec/composer.phar" SHA1 signature could not be verified: broken signature in /Users/wwx/Developer/Cellar/composer/1.2.0/libexec/composer.phar on line 23

Call Stack:
    0.0063     359032   1. {main}() /Users/wwx/Developer/Cellar/composer/1.2.0/libexec/composer.phar:0
    0.0064     359032   2. Phar::mapPhar() /Users/wwx/Developer/Cellar/composer/1.2.0/libexec/composer.phar:23

就想直接安装 master 版看看，搜了一下 homebrew 还真有真有这个参数，安装后 composer 就又可以正常运行了。

brew install composer --HEAD