Fix default clone destination
The default clone wasn't working:
$ hg clone hg
abort: repository hg/.hg not found!
This was because we were creating the destination directory from the
default, then checking whether it existed to determine whether to
expand the path.
diff -r 3903775176ed b
--- /dev/null
+++ b/b
@@ -0,0 +1,1 @@
+123
diff -r 3903775176ed b
--- /dev/null
+++ b/b
@@ -0,0 +1,1 @@
+123