当前的readme.txt内容：
Git is a distributed version control system. Git is free software distributed under the GPL. Git has a mutable index called stage.对其做一个修改：
Git is a distributed version control system. Git is free software distributed under the GPL. Git has a mutable index called stage. Git tracks changes.然后git add,查看git status：
$ git status On branch master Changes to be committed: (use "git reset HEAD <file>..." to unstage) modified: readme.txt再修改readme.txt：
$ cat readme.txt Git is a distributed version control system. Git is free software distributed under the GPL. Git has a mutable index called stage. Git tracks changes of files.此时git commit提交,提交的是第一次修改的，也就是提交的是存在了缓存区中的内容
$ git commit -m "git track changes" [master abc33e9] git track changes 1 file changed, 2 insertions(+), 1 deletion(-)查看此时的status：
$ 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")由于第二次的内容在工作区中，不在缓存区，所以显示第二次的修改没有被提交。
用git diff HEAD – readme.txt命令可以查看工作区（第二次修改的）和版本库（第一次修改的）里面最新版本的区别,可见第二次修改确实没有提交
diff --git a/readme.txt b/readme.txt index db28b2c..9a8b341 100644 --- a/readme.txt +++ b/readme.txt @@ -1,4 +1,4 @@ Git is a distributed version control system. Git is free software distributed under the GPL. Git has a mutable index called stage. -Git tracks changes. \ No newline at end of file +Git tracks changes of files. \ No newline at end of file