Changing Author Info in Old Git Commits

Changing the author information on old Git commits is an important skill for any developer, whether you want to fix wrong information or protect your privacy. Here is a smooth way to do it.

Step 1: Audit Your Commit History

It's important to look over your previous commits to figure out what needs to be changed before getting into the details. To get a list of all the unique author names and email addresses that go with them, use the following command:

git log --format='%an <%ae>' | sort -u

Step 2: Prepare Your Script

After identifying the outdated or incorrect author info, you'll use a script to rewrite history. This process involves the git filter-branch command, which allows you to revise previous commits extensively. Here’s a basic script template:

#!/bin/sh

# Examine log
git log --format='%an <%ae>' | sort -u

# REPLACE names and emails below!
git filter-branch --env-filter '
OLD_EMAIL="[email protected]"
OLD_NAME="oldname"
CORRECT_NAME="newname"
CORRECT_EMAIL="[email protected]"
if [ "$GIT_COMMITTER_EMAIL" = "$OLD_EMAIL" ]
then
    export GIT_COMMITTER_NAME="$CORRECT_NAME"
    export GIT_COMMITTER_EMAIL="$CORRECT_EMAIL"
fi
if [ "$GIT_COMMITTER_NAME" = "$OLD_NAME" ]
then
    export GIT_COMMITTER_NAME="$CORRECT_NAME"
    export GIT_COMMITTER_EMAIL="$CORRECT_EMAIL"
fi
if [ "$GIT_AUTHOR_EMAIL" = "$OLD_EMAIL" ]
then
    export GIT_AUTHOR_NAME="$CORRECT_NAME"
    export GIT_AUTHOR_EMAIL="$CORRECT_EMAIL"
fi
' --tag-name-filter cat -- --branches --tags

# Examine log
git log --format='%an <%ae>' | sort -u

# Push to remote
git push --force origin master

You should change this script to fit your own old and new information. It looks for matches in the author and committer fields with the old data and changes them as needed.

Step 3: Verify the Changes

After running the script, it’s good practice to verify that the changes have been applied correctly:

git log --format='%an <%ae>' | sort -u

This command will display the updated list of all unique author names and emails, allowing you to confirm the corrections.

Step 4: Push the Changes

Once you’ve confirmed the changes locally, the final step is to push these changes to your remote repository. This action requires a force push because you are rewriting history:

git push --force origin master

Important Considerations

It can be useful to change the author information on old commits, but there are some things to keep in mind:

1. Effects on Public Repositories: Changing the history of public repositories can make it hard for other people to work together. Usually, it's best to talk to your team about these things before you do them.
2. Backup Your Repository: Before you try to change history, you should always make sure you have a full backup of your repository. In case something goes wrong, this is there as a safety net.
3. Ethical Considerations: Be smart about how you use this feature. Changing the commit history should only be done for good reasons, like fixing mistakes or keeping your privacy safe.

Conclusion

You can change the author information on old Git commits, which is like having a powerful time machine. But there is a lot of responsibility that comes with very much power. Always be smart about how you use this power to keep your repository's integrity and dependability while protecting your privacy and the privacy of others.