Add contributing guidelines

README.md

@@ -27,6 +27,9 @@ documentation][visualization docs].
 
 ## Development
 
+### Contributing
+
+See [docs/contributing.rst](docs/contributing.rst).
 
 ### Testing
 

docs/contributing.rst

@@ -0,0 +1,87 @@
+==============
+ Contributing
+==============
+
+When contributing to this repository, we advise you to discuss the change you
+wish to make via an `issue <https://github.com/DataDog/dd-trace-py/issues>`_.
+
+Branches
+========
+
+Developement happens in the `master` branch. When all the features for the next
+milestone are merged, the next version is released and tagged on the `master`
+branch as `vVERSION`.
+
+Your pull request should targets the `master` branch.
+
+Once a new version is released, a `release/VERSION` branch might be created to
+support micro releases to `VERSION`. Patches should be cherry-picking from the
+`master` branch where possible — or otherwise created from scratch.
+
+
+Pull Request Process
+====================
+
+In order to be merged, a pull request needs to meet the following
+conditions:
+
+1. The test suite must pass.
+2. One of the repository Members must approve the pull request.
+3. Proper unit and integration testing must be implemented.
+4. Proper documentation must be written.
+
+Splitting Pull Requests
+=======================
+
+If you discussed your feature within an issue (as advised), there's a great
+chance that the implementation appears doable in several steps. In order to
+facilite the review process, we strongly advise to split your feature
+implementation in small pull requests (if that is possible) so they contain a
+very small number of commits (a single commit per pull request being optimal).
+
+That ensures that:
+
+1. Each commit passes the test suite.
+2. The code reviewing process done by humans is easier as there is less code to
+   understand at a glance.
+
+Internal API
+============
+
+The `ddtrace.internal` module contains code that must only be used inside
+`ddtrace` itself. Relying on the API of this module is dangerous and can break
+at anytime. Don't do it.
+
+Python Versions and Implementations Support
+===========================================
+
+The following Python implementations are supported:
+
+- CPython
+
+Versions of those implementations that are supported are the Python versions
+that are currently supported by the community.
+
+Libraries Support
+=================
+
+External libraries support is implemented in submodules of the `ddtest.contrib`
+module.
+
+Our goal is to support:
+
+- The latest version of a library.
+- All versions of a library that have been released less than 1 year ago.
+
+Support for older versions of a library will be kept as long as possible as
+long as it can be done without too much pain and backward compatibility — on a
+best effort basis. Therefore, support for old versions of a library might be
+dropped from the testing pipeline at anytime.
+
+Code Style
+==========
+
+The code style is enforced by `flake8 <https://pypi.org/project/flake8>`_, its
+configuration, and possibly extensions. No code style review should be done by
+a human. All code style enforcement must be automatized to avoid bikeshedding
+and losing time.

docs/index.rst

@@ -141,3 +141,4 @@ Indices and tables
     other_integrations
     basic_usage
     advanced_usage
+    contributing