	$ mkdir patches

	$ quilt new test.diff
	> Patch %{P}test.diff is now on top

	$ cat > test.txt
	< This is test.txt.
	$ quilt add test.txt
	> File test.txt added to patch %{P}test.diff

What happens when diff fails because of a permission error?

	$ chmod -r test.txt

	$ quilt refresh
	>~ .*diff: test\.txt: Permission denied
	> Diff failed on file 'test.txt', aborting
	$ echo %{?}
	> 1

	$ chmod +r test.txt

What happens on binary files?

	$ printf "\\002\\000\\001" > test.bin
	$ quilt add test.bin
	> File test.bin added to patch %{P}test.diff

	$ printf "\\003\\000\\001" > test.bin
	$ quilt diff -pab --no-index 2>/dev/null
	>~ (Files|Binary files) a/test\.bin and b/test\.bin differ
	$ quilt diff -pab --no-index >/dev/null
	> Diff failed on file 'test.bin', aborting
	$ echo %{?}
	> 1

	$ quilt refresh
	> Diff failed on file 'test.bin', aborting
	$ echo %{?}
	> 1
