/usr/include/bullet/BulletDynamics/ is in libbullet-dev 2.82-r2704+dfsg-2.
This file is owned by root:root, with mode 0o755.
..
/usr/include/bullet/BulletDynamics/Character/
/usr/include/bullet/BulletDynamics/Character/btCharacterControllerInterface.h
/usr/include/bullet/BulletDynamics/Character/btKinematicCharacterController.h
/usr/include/bullet/BulletDynamics/ConstraintSolver/
/usr/include/bullet/BulletDynamics/ConstraintSolver/btConeTwistConstraint.h
/usr/include/bullet/BulletDynamics/ConstraintSolver/btConstraintSolver.h
/usr/include/bullet/BulletDynamics/ConstraintSolver/btContactConstraint.h
/usr/include/bullet/BulletDynamics/ConstraintSolver/btContactSolverInfo.h
/usr/include/bullet/BulletDynamics/ConstraintSolver/btFixedConstraint.h
/usr/include/bullet/BulletDynamics/ConstraintSolver/btGearConstraint.h
/usr/include/bullet/BulletDynamics/ConstraintSolver/btGeneric6DofConstraint.h
/usr/include/bullet/BulletDynamics/ConstraintSolver/btGeneric6DofSpringConstraint.h
/usr/include/bullet/BulletDynamics/ConstraintSolver/btHinge2Constraint.h
/usr/include/bullet/BulletDynamics/ConstraintSolver/btHingeConstraint.h
/usr/include/bullet/BulletDynamics/ConstraintSolver/btJacobianEntry.h
/usr/include/bullet/BulletDynamics/ConstraintSolver/btPoint2PointConstraint.h
/usr/include/bullet/BulletDynamics/ConstraintSolver/btSequentialImpulseConstraintSolver.h
/usr/include/bullet/BulletDynamics/ConstraintSolver/btSliderConstraint.h
/usr/include/bullet/BulletDynamics/ConstraintSolver/btSolve2LinearConstraint.h
/usr/include/bullet/BulletDynamics/ConstraintSolver/btSolverBody.h
/usr/include/bullet/BulletDynamics/ConstraintSolver/btSolverConstraint.h
/usr/include/bullet/BulletDynamics/ConstraintSolver/btTypedConstraint.h
/usr/include/bullet/BulletDynamics/ConstraintSolver/btUniversalConstraint.h
/usr/include/bullet/BulletDynamics/Dynamics/
/usr/include/bullet/BulletDynamics/Dynamics/btActionInterface.h
/usr/include/bullet/BulletDynamics/Dynamics/btDiscreteDynamicsWorld.h
/usr/include/bullet/BulletDynamics/Dynamics/btDynamicsWorld.h
/usr/include/bullet/BulletDynamics/Dynamics/btRigidBody.h
/usr/include/bullet/BulletDynamics/Dynamics/btSimpleDynamicsWorld.h
/usr/include/bullet/BulletDynamics/Featherstone/
/usr/include/bullet/BulletDynamics/Featherstone/btMultiBody.h
/usr/include/bullet/BulletDynamics/Featherstone/btMultiBodyConstraint.h
/usr/include/bullet/BulletDynamics/Featherstone/btMultiBodyConstraintSolver.h
/usr/include/bullet/BulletDynamics/Featherstone/btMultiBodyDynamicsWorld.h
/usr/include/bullet/BulletDynamics/Featherstone/btMultiBodyJointLimitConstraint.h
/usr/include/bullet/BulletDynamics/Featherstone/btMultiBodyJointMotor.h
/usr/include/bullet/BulletDynamics/Featherstone/btMultiBodyLink.h
/usr/include/bullet/BulletDynamics/Featherstone/btMultiBodyLinkCollider.h
/usr/include/bullet/BulletDynamics/Featherstone/btMultiBodyPoint2Point.h
/usr/include/bullet/BulletDynamics/Featherstone/btMultiBodySolverConstraint.h
/usr/include/bullet/BulletDynamics/MLCPSolvers/
/usr/include/bullet/BulletDynamics/MLCPSolvers/btDantzigLCP.h
/usr/include/bullet/BulletDynamics/MLCPSolvers/btDantzigSolver.h
/usr/include/bullet/BulletDynamics/MLCPSolvers/btMLCPSolver.h
/usr/include/bullet/BulletDynamics/MLCPSolvers/btMLCPSolverInterface.h
/usr/include/bullet/BulletDynamics/MLCPSolvers/btPATHSolver.h
/usr/include/bullet/BulletDynamics/MLCPSolvers/btSolveProjectedGaussSeidel.h
/usr/include/bullet/BulletDynamics/Vehicle/
/usr/include/bullet/BulletDynamics/Vehicle/btRaycastVehicle.h
/usr/include/bullet/BulletDynamics/Vehicle/btVehicleRaycaster.h
/usr/include/bullet/BulletDynamics/Vehicle/btWheelInfo.h
/usr/include/bullet/BulletDynamics/btBulletDynamicsCommon.h