Add CONTRIBUTING.md for guidance on contributing

The initial guidance includes the markdown and git commit style.

Signed-off-by: Jie Yu <[email protected]>

Author: jieyu

CONTRIBUTING.md

@@ -0,0 +1,79 @@
+# How to Contribute
+
+CSI is under [Apache 2.0](LICENSE) and accepts contributions via GitHub pull requests.
+This document outlines some of the conventions on development workflow, commit message formatting, contact points and other resources to make it easier to get your contribution accepted.
+
+## Markdown style
+
+To keep consistency throughout the Markdown files in the CSI spec, all files should be formatted one sentence per line.
+This fixes two things: it makes diffing easier with git and it resolves fights about line wrapping length.
+For example, this paragraph will span three lines in the Markdown source.
+
+## Git commit
+
+### Sign your work
+
+The sign-off is a simple line at the end of the explanation for the patch, which certifies that you wrote it or otherwise have the right to pass it on as an open-source patch.
+The rules are pretty simple: if you can certify the below (from [developercertificate.org](http://developercertificate.org/)):
+
+```
+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.
+```
+
+then you just add a line to every git commit message:
+
+    Signed-off-by: Joe Smith <[email protected]>
+
+using your real name (sorry, no pseudonyms or anonymous contributions.)
+
+You can add the sign off when creating the git commit via `git commit -s`.
+
+### Commit Style
+
+Simple house-keeping for clean git history.
+Read more on [How to Write a Git Commit Message](http://chris.beams.io/posts/git-commit/) or the Discussion section of [`git-commit(1)`](http://git-scm.com/docs/git-commit).
+
+* Separate the subject from body with a blank line.
+* Limit the subject line to 50 characters.
+* Capitalize the subject line.
+* Do not end the subject line with a period.
+* Use the imperative mood in the subject line.
+* Wrap the body at 72 characters.
+* Use the body to explain what and why vs. how.
+  * If there was important/useful/essential conversation or information, copy or include a reference.
+* When possible, one keyword to scope the change in the subject (i.e. "README: ...", "tool: ...").