The warnings plugin searches the build directory and parents for a git repository, but this fails for out-of-tree-builds.

• out-of-tree build is preferred, having for ex. ${WORKSPACE}/src for sources and ${WORKSPACE}/build for build output.
• the build runs in the build directory, hence paths are based on it and the warningsplugin should run from this directory
• switching across agents/docker containers could make things even harder (need to stash/unstash).

eg. "checkout agent" checks out from git, stashes sources without the .git database (or might make a shallow clone).
"build agent" unstashes sources, starts a docker container for the build and runs the warning plugin afterwards.

I dont have a perfect solution, but having a parameter for either adding the path to the git repository on disk would help. even better would be to give the plugin the repository + commit information so it can pull more stuff if needed.