How to split a Git subdirectory into a new repo

Jul 29, 2024

First, install git-filter-repo. This is a python script, with no dependencies.

It's easy to install. Just drop the script somewhere in your PATH. For me:

curl "https://raw.githubusercontent.com/newren/git-filter-repo/main/git-filter-repo" -o ~/.local/bin/git-filter-path

An important thing to note is that git-filter-repo will replace all other files in the repo with those in the subdir. You should operate on a fresh copy of your repo to avoid losing data.

Let's imagine our repo looks like the following

🦄 ls -l
.rw-r--r-- ellie staff  0 B Mon Jul 29 14:13:39 2024 LICENSE
.rw-r--r-- ellie staff  0 B Mon Jul 29 14:13:34 2024 README.md
drwxr-xr-x ellie staff 64 B Mon Jul 29 14:13:35 2024 src/
drwxr-xr-x ellie staff 64 B Mon Jul 29 14:13:43 2024 subdir/

And we'd like to turn the contents subdir into its own repository.

We would run

git filter-repo --subdirectory-filter subdir

Rewriting commit messages

I generally follow conventional commits, so I had a bunch of scoped commits like this

feat(subdir): do a thing

Now that subdir is its own repo, those commits felt a bit weird. Let's tidy them up!

git filter-repo --message-callback '
      return re.sub(b"\(subdir\)\n", b"", message, flags=re.MULTILINE)
      '