This is a mini howto on moving a subdirectory to its own repository retaining history
Assume PARENT is the original parent Git repository (locally) and CHILD is the new local repository that you wish to create from a subdirectory, retaining all of its history from the PARENT repository; PARENT_PATH and CHILD_PATH are the paths to PARENT and CHILD respectively; SUBDIR is the relative path within the repository under extraction:
git clone --no-hardlinks PARENT_PATH CHILD_PATHpushd CHILD_PATH