Commits MUST be submitted only with a sign-off by the submitter. A commit without a sign-off will be automatically rejected. You don't need be the author or the copyright holder of the contribution, but you must make sure that you have the power to submit on behalf of those who are.
To sign your work, just add a line like this at the end of your commit message:
Signed-off-by: Jane Doe <firstname.lastname@example.org>
This could be done automatically in the
git commit --signoff -m "comment"
By doing this you state that you certify the following (from https://developercertificate.org):
Developer Certificate of Origin
Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
1 Letterman Drive
San Francisco, CA, 94129
Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.
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
(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.