Had Lincoln not intended to start the war, he would have ordered the evacuation of that utterly useless fort as various US Government officials had been telling the South would happen soon.
In fact, it was so certain that the "National Republican", (Official Newspaper of the Republican Party") announced the Fort was to be evacuated.
Again opinion masquerading as fact. But if you want facts then here:
Fact: Sumter was the property of the U.S. government and the South had no legal claim to it.
Fact: the garrison at Sumter took no hostile actions against the Confederacy until they started the bombardment. This in spite of at least two prior occurrences of rebel batteries firing on ships and in the face of the rebel attempt to starve them into surrender.
Fact: Lincoln made his intentions clear to Governor Pickens before the resupply effort sailed. Only food and supplies would be landed and no men and munitions unless the resupply was opposed.
Fact: when faced with a continuation of the status quo, Davis chose to start a war.