sha1_file.c: document a bunch of functions defined in the file

diff --git a/RelNotes b/RelNotes
index 00e77229ddadcb8a13b10b693a96bd76a4cb9f33..bb52cf9476df53ddb9788f16082e2e92e76a4db5 120000 (symlink)
--- a/RelNotes
+++ b/RelNotes
@@ -1 +1 @@
-Documentation/RelNotes-1.7.1.txt
\ No newline at end of file
+Documentation/RelNotes/1.9.0.txt
\ No newline at end of file