Discarding changes and unstaging

One of the benefits of using a version control system is that it is very easy to inspect the history of changes to a given file, as well as to undo changes we did not intend to make. For example, edit test.txt to remove all its contents. git status will tell us this:

On branch main
Your branch is up to date with 'origin/main'.

Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git restore <file>..." to discard changes in working directory)
        modified:   test.txt
          
no changes added to commit (use "git add" and/or "git commit -a")

If we want to see what we have changed in the test.txt file since our last commit, we can use git diff to output the changes to the terminal. Run git diff test.txt. You should see something like this:

diff --git a/test.txt b/test.txt
index bf87536..e69de29 100644
--- a/test.txt
+++ b/test.txt
@@ -1,3 +0,0 @@
-Hello, World!
-
-Git is pretty cool.
\ No newline at end of file

In the output above, lines that begin with - indicate content that has been removed from test.txt, while lines that begin with + indicate content that has been added to test.txt. We only deleted lines from the file, so there should be no lines beginning with + in the output.

VSCode Tip

To view the changes that you have made to test.txt in the VSCode window, you can click on the Source Code icon and then click on the file in the dropdown. VSCode will display a new file tab with two versions of the file, the previous version last committed and the new version with color-coded highlights to identify modifications.

If we want to discard the changes we made to test.txt, all we have to do is follow the helpful advice provided by git status:

git restore test.txt

In older versions of Git, git status may refer to the git checkout command. In that case, run this command instead:

git checkout -- test.txt

If you open test.txt after running git restore, you’ll see that its contents have been magically restored!

Now, edit test.txt and README.md to add an additional line with the text Hopefully our last change.... Run git add -u but don’t commit it just yet. git status will show this:

On branch main
Your branch is up to date with 'origin/main'.

Changes to be committed:
  (use "git restore --staged <file>..." to unstage)
        modified:   README.md
        modified:   test.txt

Now, let’s say we realized we want to commit the changes to README.md, but not to test.txt. However, we’ve already told git that we want to include test.txt in the commit. Fortunately, we can “un-include” it (or “unstage” it, in Git lingo) by running this:

git restore --staged test.txt

In older versions of Git, git status may refer to the git reset command. In that case, run this command instead:

git reset HEAD test.txt

Now, git status will show the following:

On branch main
Your branch is up to date with 'origin/main'.

Changes to be committed:
  (use "git restore --staged <file>..." to unstage)
        modified:   README.md

Changes not staged for commit:
  (use "git add <file>..." to update what will be committed)
  (use "git restore <file>..." to discard changes in working directory)
        modified:   test.txt

Go ahead and run git commit -m "Update README.md". The commit will now include only README.md.

Before moving on to the exercises of the lab, let’s make sure all our changes have been committed and pushed:

git add -u
git commit -m "Wrapping up guided part of the lab"
git push

Before continuing, make sure git status shows this:

On branch main
Your branch is up to date with 'origin/main'.

nothing to commit, working tree clean

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