follow the advisor: add DCO and some improvements

Author: lunny

CONTRIBUTING.md

@@ -8,13 +8,31 @@ It assumes you have followed the
 
 Sensitive security-related issues should be reported to [security@gitea.io](mailto:security@gitea.io).
 
+## Bug reports
+
+Please search the issues on the issue tracker with a variety of keywords to
+ensure your bug is not already reported.
+
+If unique, [open an issue](https://github.com/go-gitea/gitea/issues/new)
+and answer the questions so we can understand and reproduce the problematic
+behavior.
+
+The burden is on you to convince us that it is actually a bug in Gitea. This
+is easiest to do when you write clear, concise instructions so we can reproduce
+the behavior (even if it seems obvious). The more detailed and specific you are,
+the faster we will be able to help you. Check out
+[How to Report Bugs Effectively](http://www.chiark.greenend.org.uk/~sgtatham/bugs.html).
+
+Please be kind, remember that Gitea comes at no cost to you, and you're
+getting free help.
+
 ## Discuss your design
 
 The project welcomes submissions but please let everyone know what
 you're working on if you want to change or add something to the Gitea repositories.
 
 Before starting to write something new for the Gitea project,
-please [file an issue](https://github.com/go-gitea/gitea/issues/new).
+please [file an issue](https://github.com/go-gitea/gitea/issues/new).  
 Significant changes must go through the
 [change proposal process](https://github.com/go-gitea/proposals)
 before they can be accepted.
@@ -42,6 +60,22 @@ Changes to Gitea must be reviewed before they are accepted,
 no matter who makes the change even if an owners or a maintainer.
 We use github's pull request workflow to do that and use [lgtm](http://lgtm.co) to ensure every PR is reviewed by at least 2 maintainers.
 
+## Sign your work
+
+The sign-off is a simple line at the end of the explanation for the patch. Your
+signature certifies that you wrote the patch or otherwise have the right to pass
+it on as an open-source patch. The rules are pretty simple: If you can certify
+[DCO](DCO), then you just add a line to every git commit message:
+
+```
+Signed-off-by: Joe Smith <joe.smith@email.com>
+```
+
+Please use your real name, we really dislike pseudonyms or anonymous
+contributions. We are in the opensource world without secrets. If you set your
+`user.name` and `user.email` git configs, you can sign your commit automatically
+with `git commit -s`.
+
 ## Contributors
 
 Everyone who sent a PR to Gitea that gets accepted will be as a contributor. Please send a PR to add your name to
@@ -69,7 +103,7 @@ I'm glad to be an owner of Gitea, I agree with [CONTRIBUTING](CONTRIBUTING.md).
 
 For a honor to the owners, this document will add the history owners below:
 
-2016-11-04 ~ 2017-12-31 lunny<xiaolunwen@gmail.com> tboerger<thomas@webhippie.de> bkcsoft<kim.carlbacker@gmail.com>
+2016-11-04 ~ 2017-12-31 lunny <xiaolunwen@gmail.com> tboerger <thomas@webhippie.de> bkcsoft <kim.carlbacker@gmail.com>
 
 ## Versions
 

DCO

@@ -0,0 +1,36 @@
+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.