In a git repository I'd like to change the commit message for commit abcdef1. Two branches depend on this commit, including 12-fix-a and 13-fix-b. There are also several merge commits after commit abcdef1 and I want to keep that structure, so I don't think a simple rebase will do. How can I go about this?
user
To change the commit message for commit abcdef1 in your Git repository, you can use the git rebase command with the interactive option. Here are the steps:

1. Start by creating a new branch to make the changes on:
```
git checkout -b fix-commit-message abcdef1
```

2. Then, use the interactive rebase option to modify the commit message:
```
git rebase -i abcdef1~1
```

3. This will open your default text editor with a list of the commits that are going to be rebased. You should see the commit abcdef1 at the top of the list. Change the first word of the commit message from "pick" to "reword", then save and close the file.
```
reword abcdef1 <commit message>
```

4. Git will now pause the rebasing process at the commit you want to modify. It will open another editor window to allow you to modify the commit message.

5. Git will now continue with the rebase process. If there are any conflicts, resolve them as you would during a regular rebase.

6. Once the rebase is complete, you can delete the temporary branch:
```
git branch -d fix-commit-message
```

7. Since the two branches (12-fix-a and 13-fix-b) depend on commit abcdef1, they will need to be rebased on top of the updated commit. First, checkout `12-fix-a`:
```
git checkout 12-fix-a
```

8. Rebase the branch onto the updated commit:
```
git rebase fix-commit-message
```

9. Repeat the previous two steps for `13-fix-b`

This will update the commit message for commit `abcdef1` and preserve the commit structure, while also ensuring that the dependent branches are rebased on top of the updated commit.
assistant
What if I want to use github desktop instead of command line?
user
If you prefer to use GitHub Desktop instead of the command line, you can follow these steps to change the commit message of a local commit on branch 13-fix-b that hasn't been pushed yet:

    Open GitHub Desktop and navigate to the repository that contains the commit you want to edit.

    Switch to the branch that contains the commit you want to edit (13-fix-b in this case).

    Click on the History tab to see the commit history for the branch.

    Find the commit you want to edit and click on the gear icon next to the commit to open the options menu.

    From the options menu, select "Amend Commit".

    This will open a new screen where you can edit the commit message. Make your changes and save the new message.

    Finally, click on the "Commit to <branch name>" button to save your changes.

Your commit message will now be updated for the local commit on branch 13-fix-b. Note that you should only use this method to edit commits that have not yet been pushed to a shared repository. If the commit has already been pushed, editing it can cause issues for other users.
assistant