private static void padSmaller(DiffLines leftDestination, DiffLines rightDestination) {

		// for the bigger list, we need to pad, for the other, we don't need the empty rows        
		DiffLines smallerList = null;
		DiffLines largerList = null;

		int sizeDifference = 0;
		int length = Math.min(leftDestination.size(), rightDestination.size());
		if (leftDestination.size() == length) {
			smallerList = leftDestination;
			largerList = rightDestination;
			sizeDifference = rightDestination.size() - leftDestination.size();
		}
		// right is the small list
		else {
			smallerList = rightDestination;
			largerList = leftDestination;
			sizeDifference = leftDestination.size() - rightDestination.size();
		}

		for (int i = 0; i < sizeDifference; i++) {
			int size = smallerList.size();

			// get the line opposite of the empty line we are adding
			ValidatableLine oppositeLine = largerList.get(size);
			smallerList.insertPlaceholder(oppositeLine);
		}
	}
Copies from the source to the destination all lines that are not placeholders.  If the 
two input lists are not the same after the copy, then the smaller list is padded with
placeholder lines.
Ghidra/Features/Base/src/main/java/ghidra/app/util/html/diff/DataTypeDiffBuilder.java