当我把mac升级到Sierra时，用git拉代码时报错：

Unable to negotiate with <ip> port <port>: no matching key exchange method found. Their offer: diffie-hellman-group1-sha1

原因如下：

 Because of the latest OpenSSH version, some older (legacy) encryption algorithm have been removed from the default and therefore removed by default.

发现牛逼的google已经把sha1攻下了，sha1已经不安全了，google建议使用ssh-256.here

解决：

vim /etc/ssh/ssh_config
添加
HostkeyAlgorithms ssh-dss,ssh-rsa
KexAlgorithms diffie-hellman-group1-sha1
到文件末尾

这样就好了。