src/vs/workbench/contrib/mergeEditor/browser/model/modifiedBaseRange.ts/ModifiedBaseRange/getEditForBase
class ModifiedBaseRange:	public getEditForBase(state: ModifiedBaseRangeState): { edit: LineRangeEdit | undefined; effectiveState: ModifiedBaseRangeState } {
		const diffs = concatArrays(
			state.input1 && this.input1CombinedDiff ? [{ diff: this.input1CombinedDiff, inputNumber: 1 as const }] : [],
			state.input2 && this.input2CombinedDiff ? [{ diff: this.input2CombinedDiff, inputNumber: 2 as const }] : [],
		);

		if (state.input2First) {
			diffs.reverse();
		}

		const firstDiff = elementAtOrUndefined(diffs, 0);
		const secondDiff = elementAtOrUndefined(diffs, 1);

		if (!firstDiff) {
			return { edit: undefined, effectiveState: ModifiedBaseRangeState.default };
		}
		if (!secondDiff) {
			return { edit: firstDiff.diff.getLineEdit(), effectiveState: ModifiedBaseRangeState.default.withInputValue(firstDiff.inputNumber, true) };
		}

		const result = this.combineInputs(state.input2First ? 2 : 1);
		if (result) {
			return { edit: result, effectiveState: state };
		}

		return {
			edit: secondDiff.diff.getLineEdit(),
			effectiveState: ModifiedBaseRangeState.default.withInputValue(
				secondDiff.inputNumber,
				true
			),
		};
	}