Updating
To update imgui to a public release on GitHub, do the following.
First, find the release tag you want on https://github.com/ocornut/imgui/releases/. These steps assume v1.77.
cd third_party
curl -L https://github.com/ocornut/imgui/archive/v1.77.zip > imgui.zip
unzip imgui.zip
rsync -r imgui-1.77/ imgui/ --delete
git checkout imgui/tnt
rm -rf imgui-1.77 imgui.zip
git add imgui
Make any necessary changes to tnt/CMakeLists.txt to get Filament to compile.
Please be sure to test Filament before uploading your CL.