`quilt refresh` must respect the specified file order within patch:

All files that were already in the patch must be first in the file (in
the current order), and any new file must be in alphabetic order,
after the last file that were already in the file.

	$ mkdir patches

	$ echo foo >foo
	$ echo fnord >fnord
	$ echo zulu >zulu

	$ quilt new bar
	> Patch %{P}bar is now on top

Adding two files: they are in alphabetic order
	$ quilt add fnord zulu
	> File fnord added to patch %{P}bar
	> File zulu added to patch %{P}bar

	$ echo x >>fnord
	$ echo x >>zulu
	$ quilt refresh --no-timestamps -p ab
	> Refreshed patch %{P}bar

	$ grep '^--- ' patches/bar
	> --- a/fnord
	> --- a/zulu

Add a new file: must be placed after the last one
	$ quilt add foo
	> File foo added to patch %{P}bar

	$ echo x >>foo
	$ quilt refresh --no-timestamps -p ab
	> Refreshed patch %{P}bar

	$ grep '^--- ' patches/bar
	> --- a/fnord
	> --- a/zulu
	> --- a/foo

Remove the first file: should not change the relative order of others
	$ echo fnord >fnord

	$ quilt refresh --no-timestamps -p ab
	> Refreshed patch %{P}bar

	$ grep '^--- ' patches/bar
	> --- a/zulu
	> --- a/foo

Readd the file: must now be last
	$ echo x >>fnord

	$ quilt refresh --no-timestamps -p ab
	> Refreshed patch %{P}bar

	$ grep '^--- ' patches/bar
	> --- a/zulu
	> --- a/foo
	> --- a/fnord