Add DCO + information + hook

All contributors need to run the script once at the root of the
repository to set up automatic commit signing.

Signed-off-by: Taico Aerts <t.v.aerts@tudelft.nl>

Contributing.md

@@ -174,10 +174,28 @@ The merge request template should already contain a check list for you to go thr
 
 1. Make sure your code is formatted properly.
    You can check this by using two different gradle tasks: `./gradlew spotlessCheck` and `./gradlew spotlessApply`
-2. Ensure your commit message has a title explaining what the change is and a body explaining why you made this change.
-3. Ensure your code is tested.
-4. Ensure CI passes.
-5. Ensure the significant changes you made are listed in the changelog.
+1. Ensure your commit message has a title explaining what the change is and a body explaining why you made this change.
+1. Ensure your commit message ends with a `Signed-off-by`.
+   This can be automated by running a script once following [the steps below](#signing-your-work)
+1. Ensure your code is tested.
+1. Ensure CI passes.
+1. Ensure the significant changes you made are listed in the changelog.
+
+### Signing your work ###
+**If you are brand new to Queue**, you'll need to run a script that adds `Signed-off-by` to each of your commits. This trailer means that the author agrees with the [Developer Certificate of Origin (DCO)](docs/developer-certificate-of-origin) and with licensing the work under the [AGPL v3](LICENSE). This is important for our team and our users, legally. The [setup_commit_msg_hook.sh](contributing/hooks/setup_commit_msg_hook.sh) script will setup a Git commit-msg hook that will add this trailer to all the commit messages you write in that repository. This is not as complicated as it sounds: it is similar to typing `git commit --signoff` every time you commit. Just download the script and run it once from the root folder of whatever Git repository you are in (for example, queue or labrador).
+
+The Developer Certificate of Origin (DCO) is a document that certifies you own and/or have the right to contribute the work and license it appropriately. The DCO is used instead of a [CLA (Contributor License Agreement)](https://en.wikipedia.org/wiki/Contributor_License_Agreement). With the DCO, you retain copyright of your own work. The DCO originated in the Linux community, and is used by other projects like Git and Docker. To learn more about the DCO see this [posts on elinux.org](http://elinux.org/Developer_Certificate_Of_Origin) or how [docker uses the DCO](https://blog.docker.com/2014/01/docker-code-contributions-require-developer-certificate-of-origin/).
+
+#### Commit messages ####
+Your commit messages should end with the following trailer:
+
+```
+Signed-off-by: User Name <email@address>
+```
+
+where "User Name" is the author's real (legal) name and email@address is one of the author's valid email addresses.
+
+As explained in more details above, this is easy to fix by running once the [setup_commit_msg_hook.sh](contributing/hooks/setup_commit_msg_hook.sh) script in your repository.
 
 ## Production
 Queue runs on queue.tudelft.nl (alias for queue.ewi.tudelft.nl).

contributing/hooks/setup_commit_msg_hook.sh

+#!/bin/sh
+#
+# Put this script inside the root folder of your git directory before running it.
+
+cat >.git/hooks/commit-msg <<'EOF'
+#!/bin/sh
+grep "^Signed-off-by:" "$1" || {
+	echo >>"$1"
+	echo "Signed-off-by: $(git config user.name) <$(git config user.email)>" >>"$1"
+}
+EOF
+chmod +x .git/hooks/commit-msg
\ No newline at end of file

docs/developer-certificate-of-origin

+ 
+Developer Certificate of Origin
+Version 1.1
+
+Copyright (C) 2004, 2006 The Linux Foundation and its contributors.
+660 York Street, Suite 102,
+San Francisco, CA 94110 USA
+
+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
+    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.