MQ: tidy up if a qpush is interrupted.
This aborts the transaction, makes sure the dirtied dirstate isn't
written out, and cleans up the working directory.
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