Add test to verify same file 'extends' optimization
Add test to verify same file 'extends' optimization

Signed-off-by: Aleksandr Mezin <76c1e6be84a1d2145428706eb61f38549c50daf3@gmail.com>

thaJeztah/compose,vdemeester/compose,thaJeztah/compose,vdemeester/compose