added .branch to .gitignore
Don't create two snapshots in the same second.

This can only happen if all of the follwing are true:

	(a) source and destination directories are small
	(b) rsync completes successfully within one second
	(c) At most two snapshots are missing

In this case the rename() call which changes the snapshot name from
*-incomplete to the proper name fails for the second snapshot with
EEXIST. This is because the previous snapshot name coincides with
the name of the second snapshot.

The fix is a bit ugly but also non-invasive and simple: Just sleep
one second in this case.
Reject insane number of intervals.

Nobody needs more than 2^30 snapshots. More importantly, values
larger than 32 for --num_intervals cause an integer overflow in
desired_number_of_snapshots() because the number of snapshots in
interval zero does not fit in an unsigned int in this case.

This patch adds a test to check_config() that rejects values larger
than 30 for the --num_intervals option.

Many thanks to Klaus Kopec for pointing out this bug.
Merge branch 't/zero-rsync-fix'
Merge branch 'master' of git.ratschlab.org:software/dss
Merge branch 'master' of git://git.tuebingen.mpg.de/dss
changed : to -