Documentation/SubmittingPatches: What's Acked-by and Tested-by?

We used to talk about "internal company procedures", but this
document is about submitting patches to the git mailing list.

More useful information is when to say Acked-by: and Tested-by:.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/SubmittingPatches

@@ -216,10 +216,18 @@ then you just add a line saying
 This line can be automatically added by git if you run the git-commit
 command with the -s option.
 
-Some people also put extra tags at the end.  They'll just be ignored for
-now, but you can do this to mark internal company procedures or just
-point out some special detail about the sign-off.
-
+Notice that you can place your own Signed-off-by: line when
+forwarding somebody else's patch with the above rules for
+D-C-O.  Indeed you are encouraged to do so.  Do not forget to
+place an in-body "From: " line at the beginning to properly attribute
+the change to its true author (see (2) above).
+
+Some people also put extra tags at the end.
+
+"Acked-by:" says that the patch was reviewed by the person who
+is more familiar with the issues and the area the patch attempts
+to modify.  "Tested-by:" says the patch was tested by the person
+and found to have the desired effect.
 
 ------------------------------------------------
 MUA specific hints