Split a Git commit into multiple commits

I've often found myself, especially when working on larger feature branches, in a situation where I've made a commit that should have been split into multiple smaller commits. This can happen for various reasons, such as including unrelated changes in a single commit or realizing that a commit should have been broken down into smaller, more focused commits.

While it might sound a little intimidating, it's a fairly straightforward process so long as you're familiar with Git's interactive rebase feature. All you need to do is find the commit you want to split and then mark it with edit to stop the rebase process. Once you've done that, you can use git reset HEAD^ to unstage your changes and then commit them separately. Let's take a look at an example.

# 1. Use git rebase -i <commit>
git rebase -i HEAD~2

# 2. Mark the commit you want to split with `edit`
edit 3050fc0de Fix network bug
pick 7b1e3f2a2 Update README
# 3. Save and close the editor to start the rebase

# Stopped at 3050fc0...  Fix network bug
# You can amend the commit now, with
#
#   git commit --amend
#
# Once you are satisfied with your changes, run
#
#   git rebase --continue

# 4. Use `git reset HEAD^` to unstage the changes
git reset HEAD^
# Unstaged changes after reset:
# M       src/sever/network.js
# M       src/public/index.html
# M       package.json

# 5. Commit the changes separately
git add src/server/network.js
git commit -m 'Fix network bug'
# [detached HEAD 1f3e4d5] Fix network bug
#  1 file changed, 3 insertions(+)

git add src/public/index.html
git commit -m 'Update documentation'
# [detached HEAD 9a8b7c6] Update documentation
#  1 file changed, 62 insertions(+)

git add package.json
git commit -m 'Update dependencies'
# [detached HEAD 6d5c4b3] Update dependencies
#  2 files changed, 737 insertions(+), 802 deletions(-)

# 6. Continue the rebase
git rebase --continue
# Successfully rebased and updated refs/heads/network-bug.

# Check the log to confirm the changes
git log --oneline --decorate -4
# 1f3e4d5 (HEAD -> network-bug) Fix network bug
# 9a8b7c6 Update documentation
# 6d5c4b3 Update dependencies
# 7b1e3f2 Update README

And there you have it! Without too much hassle, you've successfully split a commit into multiple smaller commits. This process can be easily adapted to suit your needs and it can also be repeated as much as you like. Just remember to be careful when rewriting Git history, especially if you're working on a shared branch.