tests: new test for mq qdiff command
`hg qdiff .' is supposed to work but it is currently broken.
This test should help us verify when it gets fixed.
EVERYTHING
diff -r ec612a6291f1 alpha/one
--- a/alpha/one
+++ b/alpha/one
@@ -0,0 +1,1 @@
+1
diff -r ec612a6291f1 beta/two
--- a/beta/two
+++ b/beta/two
@@ -0,0 +1,1 @@
+2
BETA ONLY
diff -r ec612a6291f1 beta/two
--- a/beta/two
+++ b/beta/two
@@ -0,0 +1,1 @@
+2
INSIDE BETA
diff -r ec612a6291f1 beta/two
--- a/beta/two
+++ b/beta/two
@@ -0,0 +1,1 @@
+2