Change an old commit

Sometimes you might need to change an old commit. For example, I recently noticed I'd included an api in a commit. I don;t want people seeing that so deleting it in a new commit isn't enough. It would still be in the commit hostory if I did that so I needed a way to remove as if it had never been there.

I've written a note about amending the last commit. These steps are for changing a commit that is older than that.

You need the commit id, for example 199c527027, for the commit you want to change. You can find this by using the git log command or going to GitHub and finding it there.

Then we are going to use the interactive rebase function. So enter

git rebase --interactive '199c527027^'

Putting your commit id where I've got 199c527027. Note the ^ at the end of the identifier. This tells git to start from the commit before the commit you care about.

The default editor will open and you'll see something like this.

pick 199c527 Add markdown extension to embed tweets in notes
pick 34d2aff Write note on embedding tweets in markdown
pick f0320a1 Rebuilt sqlite db 2023-01-20
pick 32fd58f make sure there is a h1 tag on note pages
pick aa0dalb images in notes should be max 100% width

This lists all the commits between the commit you care about and now - the latest.

Edit the line for the commit you are going to change. Change pick to edit.

Then save and exit (esc then :wq if in vi).

Now make your edits.

Once you've finished add the edited files. E.g. git add <file-name>.

Then run,

git commit --amend

This will replace the commit with your new one.

Then run

git rebase --continue

to complete the rebasing process.

Now you are done.

If you are pushing to GitHub you'll need to use the --force command. E.g.

git push -f origin main