Test the patch merging functionality of `quilt diff'.

	$ mkdir d
	$ cd d

	$ cat > abc.txt
	< a
	< b
	< c

	$ mkdir patches
	$ cat > patches/series
	< a.diff
	< b.diff
	< c.diff

	$ cat > patches/a.diff
	< --- merge.orig/abc.txt
	< +++ merge/abc.txt
	< @@ -1 +1 @@
	< -a
	< +a+

	$ cat > patches/b.diff
	< --- merge.orig/abc.txt
	< +++ merge/abc.txt
	< @@ -2 +2 @@
	< -b
	< +b+

	$ cat > patches/c.diff
	< --- merge.orig/abc.txt
	< +++ merge/abc.txt
	< @@ -3 +3 @@
	< -c
	< +c+

	$ quilt push -qa
	> Applying a
	> Applying b
	> Applying c
	> Now at patch c

	$ quilt diff -P b.diff | grep -v "^\\(---\\|+++\\)"
	> Index: d/abc.txt
	> ===================================================================
	> @@ -1,3 +1,3 @@
	>  a+
	> -b
	> +b+
	>  c
	> More recent patches modify files in b.

	$ quilt diff -c a.diff -P b.diff | grep -v "^\\(---\\|+++\\)"
	> Index: d/abc.txt
	> ===================================================================
	> @@ -1,3 +1,3 @@
	> -a
	> -b
	> +a+
	> +b+
	>  c
	> More recent patches modify files in b.

	$ quilt diff -c b.diff | grep -v "^\\(---\\|+++\\)"
	> Index: d/abc.txt
	> ===================================================================
	> @@ -1,3 +1,3 @@
	>  a+
	> -b
	> -c
	> +b+
	> +c+

	$ quilt diff -c - | grep -v "^\\(---\\|+++\\)"
	> Index: d/abc.txt
	> ===================================================================
	> @@ -1,3 +1,3 @@
	> -a
	> -b
	> -c
	> +a+
	> +b+
	> +c+

	$ cd ..
	$ rm -rf d