This performs permanent modification to your git repository! Be careful.

raco pkg install git-slice

$ cd my-repo
$ racket -l git-slice subdir

This destructively updates my-repo to only include subdir.

It performs multiple steps, which can be split out as follows:

$ mkdir /path/to/tmp-data
$ cd my-repo
$ racket -l git-slice/compute subdir /path/to/tmp-data
$ racket -l git-slice/filter /path/to/tmp-data
$ racket -l git-slice/chop /path/to/tmp-data

The git-slice/filter and git-slice/chop steps can take a long time. They can be sped up by using a ramdisk: see here for Linux instructions to set one up, and then add -d /tmp/ramdisk/scratch as an additional argument. This is also supported for the git-slice command itself. The provided path must not yet exist.

git-slice can be provided a second argument for a temporary directory to use to store metadata files. If not provided, a temporary directory is created. This directory is not removed after slicing.

The --dry-run command can be provided to any command to see what it would do without doing any permanent damage.