[PATCH 4/6] SubmittingPatches: document Based-on-patch-by trailer

[kristofferhaugsbakk@fastmail.com]

From: Kristoffer Haugsbakk <code@khaugsbakk.name>

This trailer comes up often enough and the use case is not fully covered
by the other trailers here. For example, it is sometimes better to use
this trailer instead of `Co-authored-by:`.

Signed-off-by: Kristoffer Haugsbakk <code@khaugsbakk.name>
---

Notes (series):
    Note: “*can be* used”. Not “is”. Based on practical usage, I think
    it would be wrong to claim that someone sending a literal patch
    snippet via email means that this is the tag that you ought to
    use. I think e.g. `Helped-by` might be used instead.
    
    I also think that the “is” for `Helped-by` is too strongly worded
    for the same reasons.

 Documentation/SubmittingPatches | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/Documentation/SubmittingPatches b/Documentation/SubmittingPatches
index 5dc32128883..c1d12e38b28 100644
--- a/Documentation/SubmittingPatches
+++ b/Documentation/SubmittingPatches
@@ -465,6 +465,10 @@ These are the common trailers in use:
   and found it to have the desired effect.
 . `Co-authored-by:` is used to indicate that people exchanged drafts
    of a patch before submitting it.
+. `Based-on-patch-by:` can be used when someone else authored parts of
+  the patch that you are submitting. This might be relevant if someone
+  sent a patch to the mailing list without a commit message or a
+  `Signed-off-by:` and you have picked it up.
 . `Helped-by:` is used to credit someone who suggested ideas for
   changes without providing the precise changes in patch form.
 . `Mentored-by:` is used to credit someone with helping develop a
-- 
2.54.0.22.g9e26862b904