Git: How to Modify Commit Messages?

When working with Git, you might need to modify commit messages, which can be achieved through several methods depending on whether you want to modify the most recent commit message or an earlier one.

1. Modifying the Most Recent Commit Message

If you only need to modify the most recent commit message, you can use the git commit --amend command. This command opens your default text editor, allowing you to edit the previous commit message. Steps to follow:

bash
git commit --amend

At this point, the text editor opens, displaying the previous commit message, which you can directly edit. After saving and closing the editor, the commit is updated.

Example:

Suppose my initial commit message was "Initial commit", but I want to change it to "Initial project setup". I would do the following:

1. Enter the git commit --amend command.
2. In the opened text editor, change "Initial commit" to "Initial project setup".
3. Save and close the editor.

2. Modifying Earlier Commit Messages

If you need to modify a commit message that is not the most recent, you can use the git rebase command. This is typically used for editing past history and should be used with caution, especially for commits that have been pushed to a shared repository. Steps to follow:

bash
git rebase -i HEAD~X

Here, X is the number of commits you want to go back. For example, if you want to modify one of the previous three commits, you can use HEAD~3.

After executing this command, Git displays a list of the most recent X commits. You can replace pick with reword (or its shorthand r) in front of the commit you want to modify, then save and exit the editor. After that, Git opens the editor for each commit marked with reword, allowing you to edit the commit message.

Example:

Suppose I need to modify a commit message three commits back. I would do the following:

1. Enter git rebase -i HEAD~3.
2. In the interactive list that appears, change pick to reword for the commit you want to modify.
3. Save and close the list.
4. In the editor that appears next, modify the commit message.
5. Save and close the editor.

Important Notes:

• For commits that have been pushed to a remote repository, if you modify the commit history, you need to use a force push to update the remote repository. This may affect others' work, so be particularly cautious in team projects.
• The command to force-push after modifying commit history is git push --force or git push --force-with-lease.

By following these steps, you can flexibly modify commit messages in Git.