RefUpdate: new possible result Result.IO_FAILURE
This result indicates that I/O error (beyond of IOException) occurred
during RefUpdate#update().
Hitherto behaviour was to just throw IOException and leave result with
value Result.NOT_ATTEMPTED. It was just less informative.
Fetch class from pgm package needed new conditions for printing. Other
classes were reviewed and should still work just fine.
Signed-off-by: Marek Zawirski <marek.zawirski@gmail.com>
Signed-off-by: Robin Rosenberg <robin.rosenberg@dewire.com>