Re: [PATCH v2 1/3] docs: introduce dedicated page about code provenance / sign-off

["Michael S. Tsirkin" <mst@redhat.com>]

On Thu, May 16, 2024 at 05:22:28PM +0100, Daniel P. Berrangé wrote:
> Currently we have a short paragraph saying that patches must include
> a Signed-off-by line, and merely link to the kernel documentation.
> The linked kernel docs have a lot of content beyond the part about
> sign-off an thus are misleading/distracting to QEMU contributors.
> 
> This introduces a dedicated 'code-provenance' page in QEMU talking
> about why we require sign-off, explaining the other tags we commonly
> use, and what to do in some edge cases.
> 
> Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> ---
>  docs/devel/code-provenance.rst    | 212 ++++++++++++++++++++++++++++++
>  docs/devel/index-process.rst      |   1 +
>  docs/devel/submitting-a-patch.rst |  19 +--
>  3 files changed, 215 insertions(+), 17 deletions(-)
>  create mode 100644 docs/devel/code-provenance.rst
> 
> diff --git a/docs/devel/code-provenance.rst b/docs/devel/code-provenance.rst
> new file mode 100644
> index 0000000000..7c42fae571
> --- /dev/null
> +++ b/docs/devel/code-provenance.rst
> @@ -0,0 +1,212 @@
> +.. _code-provenance:
> +
> +Code provenance
> +===============
> +
> +Certifying patch submissions
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +The QEMU community **mandates** all contributors to certify provenance of
> +patch submissions they make to the project. To put it another way,
> +contributors must indicate that they are legally permitted to contribute to
> +the project.
> +
> +Certification is achieved with a low overhead by adding a single line to the
> +bottom of every git commit::
> +
> +   Signed-off-by: YOUR NAME <YOUR@EMAIL>
> +
> +The addition of this line asserts that the author of the patch is contributing
> +in accordance with the clauses specified in the
> +`Developer's Certificate of Origin <https://developercertificate.org>`__:

Why are you linking to this one?
It's slightly different from kernel, with copyright and prohibition to change it.

there's also a bit more text in the kernel, e.g. the rule against
anonymous contributions.



> +.. _dco:
> +
> +::
> +  Developer's Certificate of Origin 1.1
> +  By making a contribution to this project, I certify that:
> +
> +  (a) The contribution was created in whole or in part by me and I
> +      have the right to submit it under the open source license
> +      indicated in the file; or
> +
> +  (b) The contribution is based upon previous work that, to the best
> +      of my knowledge, is covered under an appropriate open source
> +      license and I have the right under that license to submit that
> +      work with modifications, whether created in whole or in part
> +      by me, under the same open source license (unless I am
> +      permitted to submit under a different license), as indicated
> +      in the file; or
> +
> +  (c) The contribution was provided directly to me by some other
> +      person who certified (a), (b) or (c) and I have not modified
> +      it.
> +
> +  (d) I understand and agree that this project and the contribution
> +      are public and that a record of the contribution (including all
> +      personal information I submit with it, including my sign-off) is
> +      maintained indefinitely and may be redistributed consistent with
> +      this project or the open source license(s) involved.
> +
> +It is generally expected that the name and email addresses used in one of the
> +``Signed-off-by`` lines, matches that of the git commit ``Author`` field.
> +
> +If the person sending the mail is not one of the patch authors, they are none
> +the less expected to add their own ``Signed-off-by`` to comply with the DCO
> +clause (c).
> +
> +Multiple authorship
> +~~~~~~~~~~~~~~~~~~~
> +
> +It is not uncommon for a patch to have contributions from multiple authors. In
> +this scenario, git commits will usually be expected to have a ``Signed-off-by``
> +line for each contributor involved in creation of the patch. Some edge cases:
> +
> +  * The non-primary author's contributions were so trivial that they can be
> +    considered not subject to copyright. In this case the secondary authors
> +    need not include a ``Signed-off-by``.
> +
> +    This case most commonly applies where QEMU reviewers give short snippets
> +    of code as suggested fixes to a patch. The reviewers don't need to have
> +    their own ``Signed-off-by`` added unless their code suggestion was
> +    unusually large, but it is common to add ``Suggested-by`` as a credit
> +    for non-trivial code.
> +
> +  * Both contributors work for the same employer and the employer requires
> +    copyright assignment.
> +
> +    It can be said that in this case a ``Signed-off-by`` is indicating that
> +    the person has permission to contribute from their employer who is the
> +    copyright holder. It is none the less still preferable to include a
> +    ``Signed-off-by`` for each contributor, as in some countries employees are
> +    not able to assign copyright to their employer, and it also covers any
> +    time invested outside working hours.
> +
> +When multiple ``Signed-off-by`` tags are present, they should be strictly kept
> +in order of authorship, from oldest to newest.
> +
> +Other commit tags
> +~~~~~~~~~~~~~~~~~
> +
> +While the ``Signed-off-by`` tag is mandatory, there are a number of other tags
> +that are commonly used during QEMU development:
> +
> + * **``Reviewed-by``**: when a QEMU community member reviews a patch on the
> +   mailing list, if they consider the patch acceptable, they should send an
> +   email reply containing a ``Reviewed-by`` tag. Subsystem maintainers who
> +   review a patch should add this even if they are also adding their
> +   ``Signed-off-by`` to the same commit.
> +
> + * **``Acked-by``**: when a QEMU subsystem maintainer approves a patch that
> +   touches their subsystem, but intends to allow a different maintainer to
> +   queue it and send a pull request, they would send a mail containing a
> +   ``Acked-by`` tag. Where a patch touches multiple subsystems, ``Acked-by``
> +   only implies review of the maintainers' own areas of responsibility. If a
> +   maintainer wants to indicate they have done a full review they should use
> +   a ``Reviewed-by`` tag.
> +
> + * **``Tested-by``**: when a QEMU community member has functionally tested the
> +   behaviour of the patch in some manner, they should send an email reply
> +   containing a ``Tested-by`` tag.
> +
> + * **``Reported-by``**: when a QEMU community member reports a problem via the
> +   mailing list, or some other informal channel that is not the issue tracker,
> +   it is good practice to credit them by including a ``Reported-by`` tag on
> +   any patch fixing the issue. When the problem is reported via the GitLab
> +   issue tracker, however, it is sufficient to just include a link to the
> +   issue.
> +
> + * **``Suggested-by``**: when a reviewer or other 3rd party makes non-trivial
> +   suggestions for how to change a patch, it is good practice to credit them
> +   by including a ``Suggested-by`` tag.
> +
> +Subsystem maintainer requirements
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +When a subsystem maintainer accepts a patch from a contributor, in addition to
> +the normal code review points, they are expected to validate the presence of
> +suitable ``Signed-off-by`` tags.
> +
> +At the time they queue the patch in their subsystem tree, the maintainer
> +**must** also then add their own ``Signed-off-by`` to indicate that they have
> +done the aforementioned validation. This is in addition to any of their own
> +``Reviewed-by`` tags the subsystem maintainer may wish to include.
> +
> +Tools for adding ``Signed-off-by``
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +There are a variety of ways tools can support adding ``Signed-off-by`` tags
> +for patches, avoiding the need for contributors to manually type in this
> +repetitive text each time.
> +
> +git commands
> +^^^^^^^^^^^^
> +
> +When creating, or amending, a commit the ``-s`` flag to ``git commit`` will
> +append a suitable line matching the configuring git author details.
> +
> +If preparing patches using the ``git format-patch`` tool, the ``-s`` flag can
> +be used to append a suitable line in the emails it creates, without modifying
> +the local commits. Alternatively to modify all the local commits on a branch::
> +
> +  git rebase master -x 'git commit --amend --no-edit -s'
> +
> +emacs
> +^^^^^
> +
> +In the file ``$HOME/.emacs.d/abbrev_defs`` add::
> +
> +  (define-abbrev-table 'global-abbrev-table
> +    '(
> +      ("8rev" "Reviewed-by: YOUR NAME <your@email.addr>" nil 1)
> +      ("8ack" "Acked-by: YOUR NAME <your@email.addr>" nil 1)
> +      ("8test" "Tested-by: YOUR NAME <your@email.addr>" nil 1)
> +      ("8sob" "Signed-off-by: YOUR NAME <your@email.addr>" nil 1)
> +     ))
> +
> +with this change, if you type (for example) ``8rev`` followed by ``<space>``
> +or ``<enter>`` it will expand to the whole phrase.
> +
> +vim
> +^^^
> +
> +In the file ``$HOME/.vimrc`` add::
> +
> +  iabbrev 8rev Reviewed-by: YOUR NAME <your@email.addr>
> +  iabbrev 8ack Acked-by: YOUR NAME <your@email.addr>
> +  iabbrev 8test Tested-by: YOUR NAME <your@email.addr>
> +  iabbrev 8sob Signed-off-by: YOUR NAME <your@email.addr>
> +
> +with this change, if you type (for example) ``8rev`` followed by ``<space>``
> +or ``<enter>`` it will expand to the whole phrase.
> +
> +Re-starting abandoned work
> +~~~~~~~~~~~~~~~~~~~~~~~~~~
> +
> +For a variety of reasons there are some patches that get submitted to QEMU but
> +never merged. An unrelated contributor may decide (months or years later) to
> +continue working from the abandoned patch and re-submit it with extra changes.
> +
> +The general principles when picking up abandoned work are:
> +
> + * Continue to credit the original author for their work, by maintaining their
> +   original ``Signed-off-by``
> + * Indicate where the original patch was obtained from (mailing list, bug
> +   tracker, author's git repo, etc) when sending it for review
> + * Acknowledge the extra work of the new contributor by including their
> +   ``Signed-off-by`` in the patch in addition to the orignal author's
> + * Indicate who is responsible for what parts of the patch. This is typically
> +   done via a note in the commit message, just prior to the new contributor's
> +   ``Signed-off-by``::
> +
> +    Signed-off-by: Some Person <some.person@example.com>
> +    [Rebased and added support for 'foo']
> +    Signed-off-by: New Person <new.person@mycorp.test>
> +
> +In complicated cases, or if otherwise unsure, ask for advice on the project
> +mailing list.
> +
> +It is also recommended to attempt to contact the original author to let them
> +know you are interested in taking over their work, in case they still intended
> +to return to the work, or had any suggestions about the best way to continue.
> diff --git a/docs/devel/index-process.rst b/docs/devel/index-process.rst
> index 362f97ee30..b54e58105e 100644
> --- a/docs/devel/index-process.rst
> +++ b/docs/devel/index-process.rst
> @@ -13,6 +13,7 @@ Notes about how to interact with the community and how and where to submit patch
>     maintainers
>     style
>     submitting-a-patch
> +   code-provenance
>     trivial-patches
>     stable-process
>     submitting-a-pull-request
> diff --git a/docs/devel/submitting-a-patch.rst b/docs/devel/submitting-a-patch.rst
> index 83e9092b8c..2cc4d53ff6 100644
> --- a/docs/devel/submitting-a-patch.rst
> +++ b/docs/devel/submitting-a-patch.rst
> @@ -322,23 +322,8 @@ Patch emails must include a ``Signed-off-by:`` line
>  
>  Your patches **must** include a Signed-off-by: line. This is a hard
>  requirement because it's how you say "I'm legally okay to contribute
> -this and happy for it to go into QEMU". The process is modelled after
> -the `Linux kernel
> -<http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/SubmittingPatches?id=f6f94e2ab1b33f0082ac22d71f66385a60d8157f#n297>`__
> -policy.
> -
> -If you wrote the patch, make sure your "From:" and "Signed-off-by:"
> -lines use the same spelling. It's okay if you subscribe or contribute to
> -the list via more than one address, but using multiple addresses in one
> -commit just confuses things.


I gather you no longer see value in discussing this use-case?
Maybe mention in commit log, why.

> If someone else wrote the patch, git will
> -include a "From:" line in the body of the email (different from your
> -envelope From:) that will give credit to the correct author; but again,
> -that author's Signed-off-by: line is mandatory, with the same spelling.
> -
> -There are various tooling options for automatically adding these tags
> -include using ``git commit -s`` or ``git format-patch -s``. For more
> -information see `SubmittingPatches 1.12
> -<http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/SubmittingPatches?id=f6f94e2ab1b33f0082ac22d71f66385a60d8157f#n297>`__.
> +this and happy for it to go into QEMU". For full guidance, read the
> +:ref:`code-provenance` documentation.
>  
>  .. _include_a_meaningful_cover_letter:
>  
> -- 
> 2.43.0