unpack-trees: batch fetching of missing blobs

diff --git a/RelNotes b/RelNotes
index bcb4fb98ff925389797125283e40c6e397efc1fd..80ae7a3110de6bd298cfa9d8481808d0af5e7d2d 120000 (symlink)
--- a/RelNotes
+++ b/RelNotes
@@ -1 +1 @@
-Documentation/RelNotes/1.7.11.txt
\ No newline at end of file
+Documentation/RelNotes/2.15.0.txt
\ No newline at end of file