pass failing test for 'dj' motion through a different startLine calculation depending on whether cursor is already on a newline or not

fcore/normal-mode/make-normal-delete.sml

@@ -391,7 +391,11 @@ struct
       val startIdx = Cursor.vi0 (buffer, cursorIdx)
       val buffer = LineGap.goToIdx (startIdx, buffer)
 
-      val startLine = LineGap.idxToLineNumber (cursorIdx + 1, buffer)
+      val startLine =
+        if Cursor.isCursorAtStartOfLine (buffer, startIdx) then
+          LineGap.idxToLineNumber (startIdx, buffer)
+        else
+          LineGap.idxToLineNumber (startIdx + 1, buffer)
       val endLine = startLine + count
 
       val buffer = LineGap.goToLine (endLine, buffer)
@@ -417,7 +421,11 @@ struct
       val startIdx = Cursor.vi0 (buffer, cursorIdx)
       val buffer = LineGap.goToIdx (startIdx, buffer)
 
-      val startLine = LineGap.idxToLineNumber (cursorIdx + 1, buffer)
+      val startLine =
+        if Cursor.isCursorAtStartOfLine (buffer, startIdx) then
+          LineGap.idxToLineNumber (startIdx, buffer)
+        else
+          LineGap.idxToLineNumber (startIdx + 1, buffer)
       val endLine = startLine + count + 1
 
       val buffer = LineGap.goToLine (endLine, buffer)

test/normal-delete.sml

@@ -439,7 +439,7 @@ struct
     , test "deletes two lines when cursor is on a newline" (fn _ =>
         let
           (* arrange *)
-          val originalString = "\nhello\nworld\ntrello\brillo\n"
+          val originalString = "\nhello\nworld\ntrello\nbrillo\n"
           val originalIdx = 0
 
           val app = TestUtils.init originalString