Fixes https://github.com/microsoft/vscode/issues/79910 (#80150)

Co-authored-by: NJoão Moreno <joao.moreno@microsoft.com>

extensions/git/src/staging.ts

@@ -19,7 +19,7 @@ export function applyLineChanges(original: TextDocument, modified: TextDocument,
 		// if this is a deletion at the very end of the document,then we need to account
 		// for a newline at the end of the last line which may have been deleted
 		// https://github.com/Microsoft/vscode/issues/59670
-		if (isDeletion && diff.originalStartLineNumber === original.lineCount) {
+		if (isDeletion && diff.originalEndLineNumber === original.lineCount) {
 			endLine -= 1;
 			endCharacter = original.lineAt(endLine).range.end.character;
 		}