Merge pull request microsoft#187641 from microsoft/hediet/b/musical-galliform

Fixes Diff Algorithm Bug

Author: hediet

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

@@ -52,7 +52,7 @@ export function joinSequenceDiffs(sequence1: ISequence, sequence2: ISequence, se
 
 	// First move them all to the left as much as possible and join them if possible
 	for (let i = 1; i < sequenceDiffs.length; i++) {
-		const prevResult = sequenceDiffs[i - 1];
+		const prevResult = result[result.length - 1];
 		let cur = sequenceDiffs[i];
 
 		if (cur.seq1Range.isEmpty || cur.seq2Range.isEmpty) {