Using meld for git diff

* 建立一個給git diff用的script file 在/usr/local/bin/git-meld

    #!/bin/sh
    #This file placed at /usr/local/bin/git-mled

    meld $2 $5

* 設定git diff 用的外部程式

    git config --global diff.external /usr/local/bin/git-meld

* 要恢復預設的git diff 方式

    git config --global -unset diff.external