v2v: Display a %-done progress bar when copying the disk image to the target.

This isn't quite the progress bar we have in mind, but it's sufficient
for now.

When --quiet is used, the progress bar is not displayed.

v2v/TODO

@@ -4,7 +4,7 @@ Missing features compared to Perl version:
  - Fix configure_kernel on SUSE (see Mike Latimer's email)
  - testing
 
-Progress bars for copy.
+Proper progress bars when copying.
 
 p2v:
 

v2v/v2v.ml

@@ -243,7 +243,8 @@ let rec main () =
           ?preallocation ?compat;
 
         let cmd =
-          sprintf "qemu-img convert -n -f qcow2 -O %s %s %s"
+          sprintf "qemu-img convert%s -n -f qcow2 -O %s %s %s"
+            (if not quiet then " -p" else "")
             (quote t.target_format) (quote t.target_overlay.ov_overlay_file)
             (quote t.target_file) in
         if verbose then printf "%s\n%!" cmd;