Git is a distributed version control system.

Git is free software.

$ git status

# On branch master

# Changes not staged for commit:

#   (use "git add <file>..." to update what will be committed)

#   (use "git checkout -- <file>..." to discard changes in working directory)

#

#    modified:   readme.txt

#

no changes added to commit (use "git add" and/or "git commit -a")

$ git diff readme.txt

diff --git a/readme.txt b/readme.txt

index 46d49bf..9247db6

--- a/readme.txt

+++ b/readme.txt

@@ -, +, @@

-Git is a version control system.

+Git is a distributed version control system.

 Git is free software.

git diff顾名思义就是查看difference，显示的格式正是Unix通用的diff格式，可以从上面的命令输出看到，我们在第一行添加了一个“distributed”单词。

$ git status

# On branch master

# Changes to be committed:

#   (use "git reset HEAD <file>..." to unstage)

#

#       modified:   readme.txt

#
git status告诉我们，将要被提交的修改包括readme.txt，下一步，就可以放心地提交了：

$ git commit -m "add distributed"

[master ea34578] add distributed

  file changed,  insertion(+),  deletion(-)

$ git status

# On branch master

nothing to commit (working directory clean)
Git告诉我们当前没有需要提交的修改，而且，工作目录是干净（working directory clean）的。