record: take diff lines for lack of trailing newlines into account (issue1282) The record extension incorrectly re-calculated the size lines for unified diff hunks. It counted a '\\ No newline at end of file\n' line towards the number of lines of trailing context, while it's not actually part of the context (and certainly isn't added as a line to the resulting output). Use the local name of a variable that was access through the nonlocal scope while we're at it. Seeing the variable was a little bewildering.