Nobody believe that would happen. As rustbucket has so kindly posted much of the dialogue going on in Lincoln's cabinet, it is clear that everyone expected Lincoln's fleet to start a war.
It would not have mattered what Lincoln’s intent was. Davis was not going to allow Sumter to be resupplied under any circumstance. To do so would be a political disaster for him. Lincoln could have sent open canoes loaded with hardtack, salt pork and coffee, Davis would have fired on them. He knew firing on the fort or any resupply vessels would be war. To not fire would just kick the can down the road. Sumter and Pickens were the last vestiges of the old Union left in the new Confederacy. He was determined to end that presence, if it meant war, so be it.