Each thirdparty library has a Python script for updating it. They generally:

1. Check out a thirdparty Git repository to a specific commit or tag
2. Apply patch files to the thirdparty repo to fix things specific to our build
3. Copy a subset of the thirdparty files into our repo
4. Comment out any header includes that were invalidated, if needed

upstream_utils.py contains utilities common to these update scripts.

Patches are generated in the thirdparty repo with git format-patch --no-signature so they can be applied as individual commits and easily rebased onto newer versions. Each library has its own patch directory (e.g., lib_patches).

The example below will update a hypothetical library called lib to the tag 2.0.

Start in the upstream_utils folder. Restore the original repo.

./update_lib.py

Navigate to the repo.

cd /tmp/lib

Fetch the desired version using one of the following methods.

# Fetch a full branch or tag
git fetch origin 2.0

# Fetch just a tag (useful for expensive-to-clone repos)
git fetch --depth 1 origin tag 2.0

Rebase any patches onto the new version.

git rebase 2.0

Generate patch files for the new version.

git format-patch 2.0..HEAD

Move the patch files to upstream_utils.

mv *.patch allwpilib/upstream_utils/lib_patches

Navigate back to upstream_utils

cd allwpilib/upstream_utils

Modify the version number in the call to setup_upstream_repo() in update_lib.py, then rerun update_lib.py to reimport the thirdparty files.

./update_lib.py