Fix a Commit before Creating a New Branch

2024-06-20 jms1

Our official workflow at $DAYJOB is to commit all work to a ticket-specific feature branch, and then create a pull request to get it merged into the primary branch. This allows people other than yourself to review your work before it gets merged into the main code.

I'm not perfect, sometimes I forget to create a new branch first, and accidentally create commits directly on the primary branch. Usually I realize this before pushing anything, which means I can fix it on the local machine first.

Quick Explanation

What we're going to do is this:

• Create the new branch, pointing to the last of the new commits.

• Move the main branch to point to what it was pointing at before we started creating commits.

Starting Condition

In this examples below, we're going to assume that the recent commits in the repo look like this:

$ git tree1 -a
* 67f8356 (HEAD -> main, origin/main) 2024-06-20 jms1(G) ABC-123 typo
* 8a837d6 2024-06-20 jms1(G) ABC-123 new feature
*   1d3158c 2024-06-13 jms1(G) Merge branch 'ABC-101-previous-feature'
|\
| * d60b020 (origin/ABC-101-previous-feature) 2024-06-12 jms1(G) ABC-101 previous feature
|/
* 3accd26 2024-05-29 jms1(G) ABC-93 old feature

ℹ️ git tree1

This is one of my standard git aliases.

In this case, I created two commits, 8a837d6 then 67f8356, then realized I should have created a feature branch for it first.

Create the new branch

Part of what you need to accomplish is creating a new branch, pointing to what should be the HEAD of that branch. Luckily, the current HEAD is already pointing to that commit, so if we just create the new branch here, we'll be good.

$ git branch ABC-123-new-feature

Looking at the repo after this, you can see that the new "ABC-123-new-feature" branch exists and is pointing to the correct commit.

$ git tree1 -a
* 67f8356 (HEAD -> main, origin/main, ABC-123-new-feature) 2024-06-20 jms1(G) ABC-123 typo
* 8a837d6 2024-06-20 jms1(G) ABC-123 new feature
*   1d3158c 2024-06-13 jms1(G) Merge branch 'ABC-101-previous-feature'
|\
| * d60b020 (origin/ABC-101-previous-feature) 2024-06-12 jms1(G) ABC-101 previous feature
|/
* 3accd26 2024-05-29 jms1(G) ABC-93 old feature

Move the main branch

This will "move" the head of the main branch to point to the commit that it had before we started working.

Identify the commit where the branch should point

First, identify the commit that it should be pointing to.

In this example, it should be pointing to commit 1d3158c. You can refer to the commit using its hash, or using any other branch or tag name which points to that commit. In many cases, origin/main will be usable.

Check out the main branch

$ git checkout main

At this point the repo will look like this:

$ git tree1 -a 67f8356
* 67f8356 (HEAD -> main, origin/main, ABC-123-new-feature) 2024-06-20 jms1(G) ABC-123 typo
* 8a837d6 2024-06-20 jms1(G) ABC-123 new feature
*   1d3158c 2024-06-13 jms1(G) Merge branch 'ABC-101-previous-feature'
|\
| * d60b020 (origin/ABC-101-previous-feature) 2024-06-12 jms1(G) ABC-101 previous feature
|/
* 3accd26 2024-05-29 jms1(G) ABC-93 old feature

In this particular example we were already on the main branch, so in this case this wasn't really necessary. However, you should get in the habit of using git checkout first, since that controls which branch git reset will be modifying.

Move the main branch

The git reset command changes what the current branch points to.

$ git reset --hard 1d3158c

At this point the repo will look like this:

$ git tree1 -a 67f8356
* 67f8356 (origin/main, ABC-123-new-feature) 2024-06-20 jms1(G) ABC-123 typo
* 8a837d6 2024-06-20 jms1(G) ABC-123 new feature
*   1d3158c (HEAD -> main) 2024-06-13 jms1(G) Merge branch 'ABC-101-previous-feature'
|\
| * d60b020 (origin/ABC-101-previous-feature) 2024-06-12 jms1(G) ABC-101 previous feature
|/
* 3accd26 2024-05-29 jms1(G) ABC-93 old feature

As you can see ...

• The main branch now points to the commit that it would have pointed to if we had created the new branch before creating any commits.

• The new ABC-123-new-feature branch points to the most recent commit in the work you've already done.

Keep working

At this point, the problem is fixed. You can continue working as if you had created the branch before starting, including pushing the new branch to a remote and creating a pull request.

Changelog

2024-06-20 jms1

• Created page (from notes when I actually made this mistake)