When using --notify-start or --notify-finish with many files that are able
to be downloaded quickly, the desktop notifications can cover the whole
screen (in xfce at least).

It's possible to update a desktop notification to contain some new
information. That's done when a transfer is finished, to update the start
notification. Also, if the notification has been closed, updating causes it
to re-display.

So, it would be possible to reuse desktop notifications, so only one is
displayed, and it runs through all the files that are being processed.

When only --notify-start or --notify-finish is used, the notification would
show the last thing started or finished. When both are used, the
finish notification would be quickly overwritten by the next thing started.
That seems ok?

The complication to this is jobs. With -J, it seems like it ought to
display one notification per transfer thread, so the user knows git-annex
is working on multiple things. Implementing that would need some way to get
the notification handle associated with a given Transferrer. As the code is
structured, notifyTransfer is run before the Transferrer that will be used
is known. So this would need some refactoring.

Maybe that complexity is unwarranted though? Desktip notifications only are
displayed for a short amount of time (again on xfce). So if a long-duration
download is run, the notification will appear for a short time, and then
vanish while it continues downloading. So the user is not likely to see
notifications for all the -J jobs that are running be displayed at the same
time. So reusing a single notification does not seem much worse? --[[Joey]]