Change commits for a clean log

With git commit --fixup and git rebase --autosquash you can correct a series of commits relatively easily. To demonstrate this with an example, I present the following scenario:

1. We have two commits in our my-feature branch: one for the actual function, the other for the associated tests:

   $ git log --oneline my-feature ^origin/main
   a4587fa (my-feature) Add test for my new feature
   56e34e9 Add new feature
   

2. During the merge or pull request, we receive feedback on both our function and our tests, which we would like to integrate into our existing commits. To do this, we first create temporary commits:

   $ git commit -m "Feedback on the tests from my function"
   $ git commit -m "Feedback on my function"
   $ git log --oneline my-feature ^origin/main
   556c1e8 (my-feature) Feedback on my function
   8780db6 Feedback on the tests from my function
   a4587fa Add test for my new feature
   56e34e9 Add new feature
   

… with git rebase

3. With git rebase -i we can interactively rearrange the pick lines:

   $ git rebase -i origin/main
   

   This opens our editor:

   pick 56e34e9 Add new feature
   pick a4587fa Add test for my new feature
   pick 8780db6 Feedback on the tests from my function
   pick 556c1e8 Feedback on my function
   

   We can then change the lines, for example to:

   pick 56e34e9 Add new feature
   squash 556c1e8 Feedback on my function
   pick a4587fa Add test for my new feature
   squash 8780db6 Feedback on the tests from my function
   

   Now we have two commits again:

   $ git log --oneline my-feature ^origin/main
   31a140a (my-feature) Add test for my new feature
   132ae9b Add new feature
   

4. The changes can now be sent to our remote branch with git push -f.

…with git commit --fixup and git rebase --autosquash

In Git, however, there is an even easier way to correct a previous commit: with git commit--fixup and git rebase --autosquash.

5. We create two temporary commits again, but this time with git commit--fixup:

   # Further changes to the tests
   $ git commit --fixup=31a140a
   [my-feature dd0c0d1] fixup! Add test for my new feature
    1 file changed, 1 insertion(+)
   # Further changes to my function
   $ git commit --fixup=132ae9b
   [my-function bc2298a] fixup! Add new feature
    1 file changed, 1 insertion(+)
   $ git log --oneline my-feature ^origin/main
   bc2298a (my-feature) fixup! Add new feature
   dd0c0d1 fixup! Add test for my new feature
   31a140a Add test for my new feature
   132ae9b Add new feature
   

   For commits with the --fixup=SHA option, Git writes a specially formatted commit message that can be read as this commit corrects that commit.

6. Instead of using git rebase -i to manually specify the Pick/Squash lines, we can now simply run git rebase --autosquash:

   $ git rebase --autosquash origin/main
   Successfully rebased and updated refs/heads/my-feature.
   $ git log --oneline my-feature ^origin/main
   694cb48 (my-feature) Add test for my new feature
   55cbe9b Add new feature
   

   git rebase --autosquash automates what we have just done manually with git rebase -i – but it does not open an editor in which we have to move the commits manually.

   Tip

   The --fixup option also contains the amend and reword options to reformulate the commit message, for example git commit --fixup:amend=SHA.

   Further options can be found in the Git commit documentation.