handle special case with 'k' motion: when file ends with \n\n and cursor is on first \n: we should be able to move upwards from here too

fcore/normal-mode/normal-move.sml

@@ -177,32 +177,49 @@ struct
         )
     end
 
+  fun moveCursorUpWhenOnNewline (app, buffer, newCursorLineNumber) =
+    let
+      val buffer = LineGap.goToLine (newCursorLineNumber, buffer)
+      val lineIdx = LineGap.lineNumberToIdx (newCursorLineNumber, buffer)
+
+      val lineIdx =
+        if Cursor.isPrevChrStartOfLine (buffer, lineIdx) then lineIdx
+        else lineIdx - 1
+
+      val buffer = LineGap.goToIdx (lineIdx, buffer)
+      val lineIdx = Cursor.vi0 (buffer, lineIdx)
+
+      val lineIdx = Int.max (0, lineIdx)
+    in
+      finishMoveCursorUpDown (app, newCursorLineNumber, buffer, 0, lineIdx)
+    end
+
   fun moveCursorUp (app: app_type, count) =
     let
       val {cursorIdx, buffer, ...} = app
 
-      (* calculate new idx to move to *)
       val buffer = LineGap.goToIdx (cursorIdx, buffer)
       val startOfLine = Cursor.vi0 (buffer, cursorIdx)
     in
-      if Cursor.isCursorAtStartOfLine (buffer, cursorIdx) then
+      if startOfLine = #textLength buffer - 2 then
+        (* special case: file ends with \n\n,
+         * and cursor is on first \n *)
+        let
+          val newCursorLineNumber =
+            if Cursor.isPrevChrStartOfLine (buffer, startOfLine) then
+              #lineLength buffer - 1 - count
+            else
+              #lineLength buffer - count
+          val newCursorLineNumber = Int.max (0, newCursorLineNumber)
+        in
+          moveCursorUpWhenOnNewline (app, buffer, newCursorLineNumber)
+        end
+      else if Cursor.isCursorAtStartOfLine (buffer, cursorIdx) then
         let
           val cursorLineNumber = LineGap.idxToLineNumber (cursorIdx + 1, buffer)
           val newCursorLineNumber = Int.max (0, cursorLineNumber - count)
-
-          val buffer = LineGap.goToLine (newCursorLineNumber, buffer)
-          val lineIdx = LineGap.lineNumberToIdx (newCursorLineNumber, buffer)
-
-          val lineIdx =
-            if Cursor.isPrevChrStartOfLine (buffer, lineIdx) then lineIdx
-            else lineIdx - 1
-
-          val buffer = LineGap.goToIdx (lineIdx, buffer)
-          val lineIdx = Cursor.vi0 (buffer, lineIdx)
-
-          val lineIdx = Int.max (0, lineIdx)
         in
-          finishMoveCursorUpDown (app, newCursorLineNumber, buffer, 0, lineIdx)
+          moveCursorUpWhenOnNewline (app, buffer, newCursorLineNumber)
         end
       else
         let