Don't try to rsync empty local sources

rsync/runsync.sh

@@ -60,6 +60,19 @@ fi
 if [[ "${TOOL}" == "quick-fedora-mirror" ]]; then
   su - build -c "$BINARY -d 4" 2> /local/stderr
 else
+  # If $SOURCE starts with /, let's check if it's empty or not
+  if [[ $SOURCE == /* ]]; then
+    if [[ -n "`find $SOURCE -maxdepth 0 -empty -print -quit`" ]]; then
+      # It's empty, so /afs is probably not mounted correctly. Abort!
+      RET=-1
+      cat << EOF | error | tee $OUTPUT
+      "exit_code": $RET,
+      "error": "$SOURCE empty, refusing to run",
+      "output": "$(sed 's/"/\\"/g' /local/stderr)"
+EOF
+      exit $RET
+    fi
+  fi
   $BINARY $OPTIONS $SOURCE /repo 2> /local/stderr
 fi
 RET=$?