xbps_repository_sync_index: preserve errno in error path and add debug printfs.
xbps_repository_sync_index: preserve errno in error path and add debug printfs.

datenwolf/xbps,datenwolf/xbps,stpx/xbps,stpx/xbps,ebfe/xbps,ebfe/xbps,datenwolf/xbps,ebfe/xbps,stpx/xbps