(a) A will executed after January 17, 1887, and before January 1, 1902, devising real property, from which it appears that it was the intention of the testator to devise property acquired after the execution of the will, operates as a valid devise of all after-acquired real property.
(b) A will executed after January 1, 1902, which by words of general import devises all the estate or all the property of the testator, operates as a valid devise of real property acquired by the testator after the execution of the will, unless it appears therefrom that it was not the intention of the testator to devise the after-acquired real property.