bulk-checkin: replace fast-import based implementation

diff --git a/RelNotes b/RelNotes
index 6372427426d80b01b03437fd1a55fd412fb8f75d..7d9276973af3a8f455778d2ce3ced66167f46801 120000 (symlink)
--- a/RelNotes
+++ b/RelNotes
@@ -1 +1 @@
-Documentation/RelNotes/1.7.7.txt
\ No newline at end of file
+Documentation/RelNotes/1.7.8.txt
\ No newline at end of file