How do I undo the most recent local commits in Git?

There are two ways to "undo" your last commit, depending on whether or not you have already made your commit public (pushed to your remote repository):

How to undo a local commit

Let's say I committed locally, but now I want to remove that commit.

git log
    commit 101: bad commit    # Latest commit. This would be called 'HEAD'.
    commit 100: good commit   # Second to last commit. This is the one we want.

To restore everything back to the way it was prior to the last commit, we need to reset to the commit before HEAD:

git reset --soft HEAD^     # Use --soft if you want to keep your changes
git reset --hard HEAD^     # Use --hard if you don't care about keeping the changes you made

Now git log will show that our last commit has been removed.

How to undo a public commit

If you have already made your commits public, you will want to create a new commit which will "revert" the changes you made in your previous commit (current HEAD).

git revert HEAD

Your changes will now be reverted and ready for you to commit:

git commit -m 'restoring the file I removed by accident'
git log
    commit 102: restoring the file I removed by accident
    commit 101: removing a file we don't need
    commit 100: adding a file that we need

For more information, check out Git Basics - Undoing Things.

Add/remove files to get things the way you want:

git rm classdir
git add sourcedir

Then amend the commit:

git commit --amend

The previous, erroneous commit will be edited to reflect the new index state - in other words, it'll be like you never made the mistake in the first place.

Note that you should only do this if you haven't pushed yet. If you have pushed, then you'll just have to commit a fix normally.

git rm yourfiles/*.class
git commit -a -m "deleted all class files in folder 'yourfiles'"

or

git reset --hard HEAD~1

Warning: The above command will permanently remove the modifications to the .java files (and any other files) that you wanted to commit.

The hard reset to HEAD-1 will set your working copy to the state of the commit before your wrong commit.

To change the last commit

Replace the files in the index:

git rm --cached *.class
git add *.java

Then, if it's a private branch, amend the commit:

git commit --amend

Or, if it's a shared branch, make a new commit:

git commit -m 'Replace .class files with .java files'

(To change a previous commit, use the awesome interactive rebase.)

ProTip™: Add *.class to a gitignore to stop this happening again.

To revert a commit

Amending a commit is the ideal solution if you need to change the last commit, but a more general solution is reset.

You can reset Git to any commit with:

git reset @~N

Where N is the number of commits before HEAD, and @~ resets to the previous commit.

So, instead of amending the commit, you could use:

git reset @~
git add *.java
git commit -m "Add .java files"

Check out git help reset, specifically the sections on --soft --mixed and --hard, for a better understanding of what this does.

Reflog

If you mess up, you can always use the reflog to find dropped commits:

$ git reset @~
$ git reflog
c4f708b [email protected]{0}: reset: moving to @~
2c52489 [email protected]{1}: commit: added some .class files
$ git reset 2c52489
... and you're back where you started

Use git revert <commit-id>.

To get the commit ID, just use git log.