git reset 之 soft mixed hard选项的区别

译注：为了避免丢失本地的修改以及originalHEAD，建议在进行reset操作之前，在本地创建一个新的branch，在新的branch上面进行reset，以保证master分支永远处于originalHEAD


以下为转发的正文

The reset command. Confusing. Misunderstood. Misused. But itdoesn’t need to be that way! It’s really not too confusing once youfigure out what’s going on.

Definitions

首先，让我们来解释几个定义.

First, let’s define a few terms.

HEAD（头）

指向当前branch最顶端的一个commit，该分支上一次commit后的节点

This is an alias for the tip of the current branch, which is themost recent commit you have made to that branch.

Index（索引）

The index, 也可以被认为是staging area（暂存区）,是一堆将在下一次commit中提交的文件，提交之后它就是 HEAD的父节点. （译注：git add添加的文件）

The index, also known as the staging area, is the set of filesthat will become the next commit. It is also the commit thatwill become HEAD’s parent.

Working Copy（工作副本）

当前工作目录下的文件，（译注：一般指，有修改，没有git add，没有git commit的文件）

This is the term for the current set of files you’re working onin your file system.

Flow（流程如下）

当你第一次checkout一个新的分支，HEAD指向该分支上最近一次commit。它和index和workingcopy是一样一样的。

When you first checkout a branch, HEAD points to the most recentcommit in the branch. The files in the HEAD (they aren’ttechnically files, they’re blobs but for the purposes of thisdiscussion we can think of them as straight files) match that ofthe files in the index, and the files checked out in your workingcopy match HEAD and the index as well. All 3 are in an equal state,and Git is happy.

当你修改了一个文件，Git注意到了会说“哦，有些东西被改了”，你的workingcopy不再和index和HEAD相同了，所以当文件有改动，它会标记这些文件。

When you perform a modification to a file, Git notices and says“oh, hey, something has changed. Your working copy no longermatches the index and HEAD.” So it marks the file as changed.

然后，你执行gitadd命令，这条命令会将上面修改的文件缓存在index中，Git又说了“哦，你的workingcopy和index相同了，而他们俩和HEAD不同了”。

Then, when you do a git add, it stages the file inthe index, and Git says “oh, okay, now your working copy and indexmatch, but those are both different than HEAD.”

当你执行gitcommit，Git创建了一个新的commit，HEAD这时指向这个新的commit，此时，HEAD &index & working copy又相同了，Git又开心了一次。

When you then perform a git commit, Git creates anew commit that HEAD now points to and the status of the index andworking copy match it so Git’s happy once more.

Reset

If you just look at the reset command by itself, all it does isreset HEAD (the tip of the current branch) to another commit. Forinstance, say we have a branch (the name doesn’t matter, so let’scall this one “super-duper-feature”) and it looks like so:

If we perform:

> git reset HEAD

… nothing happens. This is because we tell git to reset thisbranch to HEAD, which is where it already is. But if we do:

> git reset HEAD~1

(HEAD~1 is shorthand case for “the commit right before HEAD”, orput differently “HEAD’s parent”) our branch now looks like so:

If we start at the latest commit again and do:

> git reset HEAD~2

our branch would look like so:

Again, all it does on a basic level is move HEAD to anothercommit.

Parameters

reset命令本身很简单，但是它的参数让人迷惑，主要的参数有soft,hard and mixed，它们告诉Git，当执行reset时，要对index和workingcopy做什么。

So the reset command itself is pretty simple, but it’s theparameters that cause confusion. The main parameters aresoft,hard and mixed. Thesetell Git what to do with your index and working copy whenperforming the reset.

Soft

The--soft参数只告诉Git将其他的commit重置到HEAD，就仅此而已。index和workingcopy中的文件都不改变。

parameter tells Git to reset HEAD to another commit, but that’sit. If you specify--soft Git will stop there andnothing else will change. What this means is that the index andworking copy don’t get touched, so all of the files that changedbetween the original HEAD and the commit you reset to appear to bestaged.

Mixed (default)

The --mixed改变HEAD和index，指向那个你要reset到的commit上。而workingcopy文件不被改变。当然会显示工作目录下有修改，但没有缓存到index中。

parameter (which is the default if you don’t specify anything)will reset HEAD to another commit,and will resetthe index to match it, but will stop there. The working copy willnot be touched. So, all of the changes between the original HEADand the commit you reset to are still in the working copy andappear as modified, but not staged.

Hard

The --hard HEAD & index & workingcopy同时改变到你要reset到的那个commit上。这个参数很危险，执行了它，你的本地修改可能就丢失了。

parameter will blow out everything – it resets HEAD back toanother commit, resets the index to match it,andresets the working copy to match it as well. This is the moredangerous of the commands and is where you can cause damage. Datamight get lost here*!

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可以用git reflog命令查看coomit ID，恢复到reset之前的状态。
* You can recover it using git reflog but that’s outof scope here.

转自：http://davidzych.com/2014/05/24/difference-between-git-reset-soft-mixed-and-hard/

http://blog.sina.com.cn/s/blog_936739790102v3nk.html