follow the advisor: add DCO and some improvements

CONTRIBUTING.md

@@ -8,6 +8,24 @@ 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
@@ -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.