servo: transmission: torrent-done: implement a TR_NO_HARDLINK option

hosts/by-name/servo/services/transmission/torrent-done

@@ -7,6 +7,7 @@
 # optionally:
 # - TR_DRY_RUN=1
 # - TR_DEBUG=1
+# - TR_NO_HARDLINK=1
 
 DOWNLOAD_DIR=/var/media/torrents
 
@@ -65,6 +66,9 @@ destructive find "$MEDIA_DIR/" -type f \(\
   -o -iname 'YTS*.com.txt' \
   \) -exec rm {} \;
 
+if ! [ -b "${TR_NO_HARDLINK}" ]; then
   # dedupe the whole media library.
-# yeah, a bit excessive: move this to a cron job if that's problematic.
+  # yeah, a bit excessive: move this to a cron job if that's problematic
+  #   or make it run with only 1/N probability, etc.
   destructive hardlink /var/media --reflink=always --ignore-time --verbose
+fi