Revision control
++ QT += widgets
++ requires(qtConfig(undoview))
++
++ HEADERS = commands.h \
++ diagramitem.h \
++ diagramscene.h \
++ mainwindow.h
++ SOURCES = commands.cpp \
++ diagramitem.cpp \
++ diagramscene.cpp \
++ main.cpp \
++ mainwindow.cpp
++ RESOURCES = undoframework.qrc
++
++ # install
++ target.path = $$[QT_INSTALL_EXAMPLES]/widgets/tools/undoframework
++ INSTALLS += target