In this section, we will explore how to revert commits in Git. Reverting commits is a crucial skill for undoing changes in a controlled manner, especially when you need to maintain a clean and stable project history.

Reverting a commit means creating a new commit that undoes the changes introduced by a previous commit. Unlike other methods of undoing changes (like git reset), reverting is a safe operation that does not alter the commit history, making it ideal for collaborative environments.

• Undoing a specific commit: When you need to undo the effects of a specific commit without affecting subsequent commits.
• Maintaining history integrity: When you want to ensure that the commit history remains intact and visible to all collaborators.
• Collaborative projects: When working in a team, reverting is safer than resetting because it avoids rewriting history.

The basic command to revert a commit is:

Let's walk through an example to understand how to revert a commit.

1. View Commit History: First, let's view the commit history to identify the commit we want to revert.

   git log --oneline
   

   Output:

   a1b2c3d (HEAD -> main) Add new feature
   e4f5g6h Fix bug in feature
   i7j8k9l Initial commit
   

2. Revert the Commit: Suppose we want to revert the commit e4f5g6h (Fix bug in feature). We use the git revert command followed by the commit hash.

   git revert e4f5g6h
   

3. Commit Message: Git will open the default text editor to allow you to edit the commit message for the revert commit. You can modify it or leave it as is, then save and close the editor.

   Default message:

   Revert "Fix bug in feature"
   
   This reverts commit e4f5g6h.
   

4. Verify the Revert: Finally, verify that the revert commit has been created.

   git log --oneline
   

   Output:

   b2c3d4e (HEAD -> main) Revert "Fix bug in feature"
   a1b2c3d Add new feature
   e4f5g6h Fix bug in feature
   i7j8k9l Initial commit
   

To revert multiple commits, you can either revert them one by one or use a range of commits. However, reverting a range of commits can be complex and may require resolving conflicts.

Exercise: Revert a Commit

1. Clone a sample repository:

   git clone https://github.com/example/sample-repo.git
   cd sample-repo
   

2. Create a new commit:

   echo "New feature" > feature.txt
   git add feature.txt
   git commit -m "Add new feature"
   

3. Create another commit:

   echo "Bug fix" > bugfix.txt
   git add bugfix.txt
   git commit -m "Fix bug in feature"
   

4. Revert the second commit:

   git revert HEAD
   

5. Verify the revert:

   git log --oneline
   

Solution:

1. The commit history should show the revert commit:

   1234567 (HEAD -> main) Revert "Fix bug in feature"
   89abcdef Add new feature
   0123456 Fix bug in feature
   

• Conflict Resolution: Reverting commits that affect the same lines of code as subsequent commits may lead to conflicts. Be prepared to resolve these conflicts manually.
• Reverting Merge Commits: Reverting a merge commit requires special handling. Use the -m option to specify the parent number.
• Commit History: Always review the commit history before reverting to ensure you are targeting the correct commit.

Reverting commits is a powerful tool in Git that allows you to undo changes while preserving the commit history. This method is particularly useful in collaborative environments where maintaining a clear and accurate history is essential. By mastering the revert command, you can effectively manage and correct changes in your projects.