Documentation/log: clarify sha1 non-abbreviation in log --raw

Signed-off-by: Matthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/pretty-formats.txt

@@ -79,7 +79,10 @@ stored in the commit object.  Notably, the SHA-1s are
 displayed in full, regardless of whether --abbrev or
 --no-abbrev are used, and 'parents' information show the
 true parent commits, without taking grafts or history
-simplification into account.
+simplification into account. Note that this format affects the way
+commits are displayed, but not the way the diff is shown e.g. with
+`git log --raw`. To get full object names in a raw diff format,
+use `--no-abbrev`.
 
 * 'format:<string>'
 +