Re: git format-patch --signoff

[Junio C Hamano <gitster@pobox.com>]

Michał Mirosław <mirq-linux@rere.qmqm.pl> writes:

> I just noticed that `git format-patch --signoff` adds the 'Signed-off-by'
> line even if the exact same line is already present in the commit message.
> Could this be avoided in the tool?
>
> git version 2.30.2
>
> Best Regards
> Michał Mirosław

The rule should be "avoid adding the same sign-off as the one at the
end".  In other words, as a record of the flow of patch custody,

    Signed-off-by: original author
    Signed-off-by: contributing editor
    Signed-off-by: original author

is perfectly reasonable for a patch originally authored, tweaked by
an editor and sent back to the author, and further improved by the
original author, while

    Signed-off-by: original author
    Signed-off-by: contributing editor
    Signed-off-by: contributing editor

sent back to the original author by the editor would not be sane, as
there is no need to repeat the same s-o-b to signal whatever it
might imply (e.g.  the editor edited the patch twice before sending
it back).

The test in t4014

  https://github.com/git/git/blob/master/t/t4014-format-patch.sh#L1561

    test_expect_success 'signoff: the same signoff at the end' '
            append_signoff <<-\EOF >actual &&
            subject

            body

            Signed-off-by: C O Mitter <committer@example.com>
            EOF
            cat >expect <<-\EOF &&
            4:Subject: [PATCH] subject
            8:
            10:
            11:Signed-off-by: C O Mitter <committer@example.com>
            EOF
            test_cmp expect actual
    '

It creates a commit with an existing S-o-b by the same person as the
one running the "format-patch --signoff" command (the append-signoff
test helper used there (1) creates a commit with the log message fed
from the standard input, (2) runs format-patch --signoff to show the
commit and emits the Subject and S-o-b lines in it.  As we can see,
we expect that the existing signoff is not followed by another copy
of the same signoff. 

This test hasn't changed since it was written in Feb 2013, and I
think 2.30.2 is recent enough to conform to the rule to pass this
test.