GNU Emacs Manual, 14.3 Automatic Scrolling:

> In case you customize multiple variables, the order of priority is: `scroll-conservatively`, then `scroll-step`, ...

It works for `next-line`, BUT ignores `previous-line`.

_____________________________________

Say evaluate the following Lisp code:

```
(setq scroll-conservatively 101)
(setq scroll-step 5)
```

Then, when calling `previous-line` which will lead to auto-scrolling,
it acts like that `scroll-conservatively` is not set,
i.e., Emacs will scroll 5 lines.

This PATCH fixes the BUG.