A series of 8 different commits has been made in your local environment. At the time these commits made sense however now they need to be just a single commit. Using Rebase we need to squash the commits together.

Using git rebase --interactive HEAD~8, we have the range of commits from HEAD to the last 0. To squash we need a base commit which everything will be squashed into. As such, leave the first commit as "pick" but change the rest to "squash".

After you save you will have the chance to edit. By default, the Git commit message will be a combination of the previously squashed commit messages.

Task

When we enter Interactive Rebase we can specify that we want to modify the previous 8 commits using git rebase --interactive HEAD~8

In the previous stage we used reword. Here we want to use squash. We want to squash 8 commits into one, if we labelled all the commits as squash then we'd get the error "Cannot 'squash' without a previous commit" as there isn't a base commit to squash everything into.

To squash the commits we need to leave the first commit as our base, and label the following 7 with squash.

Commit Message

As saving and quitting Vim we are shown a new Vim window which lists a combination of the 8 commit messages in the rebase.

After saving the commit message the history will be modfied. You can see this using git log --oneline

Re-ordering commits can help build a better picture of the logical order that worked was completed in.

Task

We want to re-order our last two commits. Using HEAD~2 allows us to modify them.

git rebase --interactive HEAD~2

Using Vim, simply reorder the lines, save & quit, and the commits will match the order.

Just like with squashing commits, sometimes it's useful to split changes out of commits in order to keep them focused and make cherry picking or reverting easier.

Splitting commits is a two staged process. First we need to define which commit we want to split and then we need to define how we want the new commits to look.

Defining Commit To Split

Here we want to split the previous commit. We enter rebase mode using git rebase --interactive HEAD~1

Like with previous rebasing, we need to change the task to edit

We are now in a state of interactively edit the history. Git will record all the changes and the end result will be applied to the repository.

Splitting Commits

After defining we want to edit the commit we are now in a state that allows us to change the history.

1. As we want to split an existing commit we first we need to remove it using git reset HEAD^.

2. The commit has been removed but the files still exist. We can now perform the commits as we previously desire, as two separate actions.

Execute the commands:

git add file3.txt
git commit -m "File 3"
git add file4.txt
git commit -m "File 4"

Saving

Once happy with the state of the repository, we tell Git to continue the rebase and update the repository with --continue.

git rebase --continue

You can see the output and the two new commits using git log --oneline