Fixes microsoft/vscode-internalbacklog#4480 (microsoft#188512)

Author: hediet

src/vs/editor/common/diff/algorithms/joinSequenceDiffs.ts

@@ -33,8 +33,11 @@ export function smoothenSequenceDiffs(sequence1: ISequence, sequence2: ISequence
 	return result;
 }
 
-export function randomRandomMatches(sequence1: LinesSliceCharSequence, sequence2: LinesSliceCharSequence, sequenceDiffs: SequenceDiff[]): SequenceDiff[] {
+export function removeRandomMatches(sequence1: LinesSliceCharSequence, sequence2: LinesSliceCharSequence, sequenceDiffs: SequenceDiff[]): SequenceDiff[] {
 	let diffs = sequenceDiffs;
+	if (diffs.length === 0) {
+		return diffs;
+	}
 
 	let counter = 0;
 	let shouldRepeat: boolean;

src/vs/editor/common/diff/standardLinesDiffComputer.ts

@@ -11,7 +11,7 @@ import { Position } from 'vs/editor/common/core/position';
 import { Range } from 'vs/editor/common/core/range';
 import { DateTimeout, ISequence, ITimeout, InfiniteTimeout, SequenceDiff } from 'vs/editor/common/diff/algorithms/diffAlgorithm';
 import { DynamicProgrammingDiffing } from 'vs/editor/common/diff/algorithms/dynamicProgrammingDiffing';
-import { optimizeSequenceDiffs, randomRandomMatches, smoothenSequenceDiffs } from 'vs/editor/common/diff/algorithms/joinSequenceDiffs';
+import { optimizeSequenceDiffs, removeRandomMatches, smoothenSequenceDiffs } from 'vs/editor/common/diff/algorithms/joinSequenceDiffs';
 import { MyersDiffAlgorithm } from 'vs/editor/common/diff/algorithms/myersDiffAlgorithm';
 import { ILinesDiffComputer, ILinesDiffComputerOptions, LineRangeMapping, LinesDiff, MovedText, RangeMapping, SimpleLineRangeMapping } from 'vs/editor/common/diff/linesDiffComputer';
 
@@ -213,7 +213,7 @@ export class StandardLinesDiffComputer implements ILinesDiffComputer {
 		diffs = optimizeSequenceDiffs(slice1, slice2, diffs);
 		diffs = coverFullWords(slice1, slice2, diffs);
 		diffs = smoothenSequenceDiffs(slice1, slice2, diffs);
-		diffs = randomRandomMatches(slice1, slice2, diffs);
+		diffs = removeRandomMatches(slice1, slice2, diffs);
 
 		const result = diffs.map(
 			(d) =>