Git author amend

There can be several use cases when you need to change author name and email in git commit history. Before sharing the solution that solved my issue, I would like to share the solution that prevents it.

How to use multiple git configuration

I am working for a customer that requires git commits are authored with my corporate email, while when I develop my side projects I want to use my GitHub nickname.

Usually I create in my user home folder, a folder named as the domain hosting the code. So for example I have folders:

• github.com
• source.my-customer.com

Now if I want to use a different git config depending on the folder, I edit my ~/.gitconfig file with something like

[includeIf "gitdir:github.com/"]
  path = /Users/myuser/github.com/.gitconfig
[includeIf "gitdir:.config/"]
  path = /Users/myuser/github.com/.gitconfig
[includeIf "gitdir:source.my-customer.com/"]
  path = /Users/myuser/source.my-customer.com/.gitconfig
[github]
  user = my-github-nickname

Where my /Users/myuser/github.com/.gitconfig is something like

[user]
  name = my-github-nickname
  email = my-github-email@example.com
[pull]
  rebase = true
[init]
  defaultBranch = main

And the /Users/myuser/source.my-customer.com/.gitconfig is something similar.

How to change git history

I found this script here at stack overflow that uses git filter-branch

#!/bin/sh

git filter-branch --env-filter '
OLD_EMAIL="your-old-email@example.com"
CORRECT_NAME="Your Correct Name"
CORRECT_EMAIL="your-correct-email@example.com"
if [ "$GIT_COMMITTER_EMAIL" = "$OLD_EMAIL" ]
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

Just replace the variables OLD_EMAIL, CORRECT_NAME and CORRECT_EMAIL with the correct values, move to the repository folder and launch it. When it is done, probably you need to force the push

git push --force

Notice that if the commits need to be changed are also on a git tag, you need to fetch it and modify it locally, delete it remotely and then push it again.