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Learn about a few different commands to switch between different versions of a Git project and when to use them. 

How to Backtrack

The __hamlet__ repository we are working on contains five files. In Git, it's common to change many files, add those files to the staging area, and commit them to a repository in a single commit. 

For example, say you want to change the character "LARRY" to "LAERTES" in the script. The name currently appears in two files. After you change the name in both files, you could add the changed files to the staging area with:

```
git add filename_1 filename_2
```

Note the word `filename` above refers to the name of the file you are adding to the staging area, such as __scene-3.txt__. 

more git add

Creating a project is like hiking in a forest. Sometimes you take a wrong turn and find yourself lost.

Just like retracing your steps on that hike, Git enables you to rewind to the part before you made the wrong turn. You can do this with:

```
git reset commit_SHA
```
This command works by using the first 7 characters of the SHA of a previous commit. For example, if the SHA of the previous commit is `5d692065cf51a2f50ea8e7b19b5a7ae512f633ba`, use: 
```
git reset 5d69206
``` 
`HEAD` is now set to that previous commit.  



git reset II

What if you decide to change the ghost's line in the working directory, but then decide you wanted to discard that change?

You could rewrite the line how it was originally, but what if you forgot the exact wording? The command
 
```
git checkout HEAD filename
```
will restore the file in your working directory to look exactly as it did when you last made a commit. 

Here, `filename` again is the actual name of the file. If the file is named **changes.txt**, the command would be 

```bash
git checkout HEAD changes.txt
```

git checkout

Great! The files you've added to the staging area belong in the same commit.

What if, before you commit, you accidentally delete an important line from __scene-2.txt__? Unthinkingly, you add __scene-2.txt__ to the staging area. The file change is unrelated to the Larry/Laertes swap and you don't want to include it in the commit. 

We can _unstage_ that file from the staging area using
 
```
git reset HEAD filename
```
This command _resets_ the file in the staging area to be the same as the `HEAD` commit. It does not discard file changes from the working directory, it just removes them from the staging area.

git reset I

In Git, the commit you are currently on is known as the `HEAD` commit. In many cases, the most recently made commit is the `HEAD` commit. 

To see the `HEAD` commit, enter:  
```
git show HEAD
```
The output of this command will display everything the <a href="https://www.codecademy.com/en/courses/learn-git/lessons/git-workflow/exercises/git-log" target=_blank>git log command</a> displays for the `HEAD` commit, plus all the file changes that were committed.    

head commit

Congratulations! You've learned three different ways to backtrack in Git. You can use these skills to undo changes made to your Git project.

Let's take a moment to review the new commands: 

* `git checkout HEAD filename`: Discards changes in the working directory.
* `git reset HEAD filename`: Unstages file changes in the staging area.
* `git reset commit_SHA`: Resets to a previous commit in your commit history. 
 
Additionally, you learned a way to add multiple files to the staging area with a single command: 

```
git add filename_1 filename_2
```

Generalizations

To better understand `git reset commit_SHA`, notice the diagram on the right. Each circle represents a commit. 

__Before reset__:
* `HEAD` is at the _most recent commit_

__After resetting__:
* `HEAD` goes to a _previously made commit_ of your choice
* The gray commits are no longer part of your project
* You have in essence rewound the project's history
 

git reset review

When working on a Git project, sometimes we make changes that we want to get rid of. Git offers a few eraser-like features that allow us to undo mistakes during project creation. In this lesson, we'll learn some of these features. 

To start out, let's review the basic Git workflow.