$ mkdir patches

$ echo foo > foo
$ quilt new 1.patch
> Patch %{P}1.patch is now on top

$ quilt add foo
> File foo added to patch %{P}1.patch

$ echo bar > foo
$ quilt refresh -p ab
> Refreshed patch %{P}1.patch

# Sabotage the series file
$ echo -n 1.patch > patches/series

# quilt should insert the missing newline before appending
$ quilt new 2.patch
> Patch %{P}2.patch is now on top
$ cat patches/series
> 1.patch
> 2.patch