一、 检测电脑上面是否安装过git

终端输入 git
如果安装过，终端的打印

WMBdeMacBook-Pro:~ WENBO$ git
usage: git [--version] [--help] [-C <path>] [-c name=value]
           [--exec-path[=<path>]] [--html-path] [--man-path] [--info-path]
           [-p | --paginate | --no-pager] [--no-replace-objects] [--bare]
           [--git-dir=<path>] [--work-tree=<path>] [--namespace=<name>]
           <command> [<args>]

These are common Git commands used in various situations:

start a working area (see also: git help tutorial)
   clone      Clone a repository into a new directory
   init       Create an empty Git repository or reinitialize an existing one

work on the current change (see also: git help everyday)
   add        Add file contents to the index
   mv         Move or rename a file, a directory, or a symlink
   reset      Reset current HEAD to the specified state
   rm         Remove files from the working tree and from the index

examine the history and state (see also: git help revisions)
   bisect     Use binary search to find the commit that introduced a bug
   grep       Print lines matching a pattern
   log        Show commit logs
   show       Show various types of objects
   status     Show the working tree status

grow, mark and tweak your common history
   branch     List, create, or delete branches
   checkout   Switch branches or restore working tree files
   commit     Record changes to the repository
   diff       Show changes between commits, commit and working tree, etc
   merge      Join two or more development histories together
   rebase     Reapply commits on top of another base tip
   tag        Create, list, delete or verify a tag object signed with GPG

collaborate (see also: git help workflows)
   fetch      Download objects and refs from another repository
   pull       Fetch from and integrate with another repository or a local branch
   push       Update remote refs along with associated objects

'git help -a' and 'git help -g' list available subcommands and some
concept guides. See 'git help <command>' or 'git help <concept>'
to read about a specific subcommand or concept.

二、通过homebrew安装Git

1、安装homebrew

/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

2、安装git

brew install git

三、移除现有Ruby默认源

$gem sources --remove https://rubygems.org/

四、使用新的源

$gem sources --add https://gems.ruby-china.com/

五、验证新源是否替换成功

$gem sources -l

六、安装CocoaPods

(1) 安装

$sudo gem install cocoapods

如果你在使用上面的这句代码的时候提示如下权限读写错误

You don't have write permissions for the /usr/bin directory.

将其替换成如下的代码，苹果系统升级 OS X EL Capitan，使用下面这个命令

$sudo gem install -n /usr/local/bin cocoapods

(2)

$pod setup

(3) 更新gem

$sudo gem update --system