all: add a CONTRIBUTING.md doc

Signed-off-by: Paul Moore <[email protected]>

Author: pcmoore

CONTRIBUTING.md

@@ -0,0 +1,107 @@
+How to Contribute to The SELinux Notebook
+===============================================================================
+https://github.com/SELinuxProject/selinux-notebook
+
+This document is intended to act as a guide to help you contribute to the
+The SELinux Notebook.  It is not perfect, and there will always be exceptions
+to the rules described here, but by following the instructions below you
+should have a much easier time getting your work merged with the upstream
+project.
+
+## Make Sure Your Changes Render Correctly
+
+The SELinux Notebook can be viewed in three different formats: Markdown, HTML,
+and PDF.  Your changes need to render correctly in all three formats.  The
+HTML and PDF formatted notebooks can be created using the included Makefile
+and Markdown can be viewed directly via the GitHub source browser or any
+number of Markdown viewers.
+
+## Explain Your Work
+
+At the top of every patch you should include a description of the change you
+are making as well as your motivation.
+
+## Sign Your Work
+
+The sign-off is a simple line at the end of the patch description, which
+certifies that you wrote it or otherwise have the right to pass it on as an
+open-source patch.  The "Developer's Certificate of Origin" pledge is taken
+from the Linux Kernel and the rules are pretty simple:
+
+	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.
+
+... then you just add a line to the bottom of your patch description, with
+your real name, saying:
+
+	Signed-off-by: Random J Developer <[email protected]>
+
+You can add this to your commit description in `git` with `git commit -s`
+
+## Post Your Patches Upstream
+
+The SELinux Notebook accepts both GitHub pull requests and patches sent via
+the SELinux developers mailing list.  GitHub pull requests are preferred.  The
+sections below explain how to contribute via either method. Please read each
+step and perform all steps that apply to your chosen contribution method.
+
+### Submitting via Email
+
+Depending on how you decided to work with the notebook sources and what
+tools you are using there are different ways to generate your patch(es).
+However, regardless of what tools you use, you should always generate your
+patches using the "unified" diff/patch format and the patches should always
+apply to the notebook source tree using the following command from the top
+directory of the notebook sources:
+
+	% patch -p1 < changes.patch
+
+If you are not using git, stacked git (stgit), or some other tool which can
+generate patch files for you automatically, you may find the following command
+helpful in generating patches, where "selinux-notebook.orig/" is the unmodified
+source code directory and "selinux-notebook/" is the source code directory with your
+changes:
+
+	% diff -purN selinux-notebook.orig/ selinux-notebook/
+
+When in doubt please generate your patch and try applying it to an unmodified
+copy of the notebook sources; if it fails for you, it will fail for the rest
+of us.
+
+Finally, you will need to email your patches to the mailing list so they can
+be reviewed and potentially merged into the main notebook repository.  When
+sending patches to the mailing list it is important to send your email in text
+form, no HTML mail please, and ensure that your email client does not mangle
+your patches.  It should be possible to save your raw email to disk and apply
+it directly to the notebook sources; if that fails then you likely have
+a problem with your email client.  When in doubt try a test first by sending
+yourself an email with your patch and attempting to apply the emailed patch to
+the notebook repository; if it fails for you, it will fail for the rest of
+us.
+
+### Submitting via GitHub
+
+See [this guide](https://help.github.com/en/github/collaborating-with-issues-and-pull-requests/creating-a-pull-request) if you've never done this before.