[sheepdog] [PATCH] Convert config file - the free disk space is now stored in the config file

[Jens WEBER]

> > To use this new feature (commit 5e39f98abf32faa340afc9b535a56391359b5234) do 
> as follow
> > 
> >   - first shutdown cluster
> >   - convert all config files with 'vnodes2autoconfig /path/to/store/config'
> >   - update to new version and start cluster again
> 
> Can we please avoid incmpatible config file changes entirely?  The new
> versions should simply have a magic that it can be detected and the C
> code should handle both.
> 

a version number of the config file would also be nice then there is less magic

struct sheepdog_config {
+	uint16_t configversion; <- what do you think
	uint64_t ctime;
	uint64_t space;
	uint16_t flags;
	uint8_t copies;
	uint8_t store[STORE_LEN];
};