Clarify core developer responsibilities (#95)

ncoghlan · web-flow · commit 13e6f2e93d3b · 2017-01-19T10:33:15.000+11:00
We don't clearly document anywhere the additional expectations
that apply to core developers merging changes that don't apply
to folks contributing in other ways.

This new section is an initial step in addressing that omission.
diff --git a/coredev.rst b/coredev.rst
@@ -18,6 +18,44 @@ a while to make sure you understand the development process. If other core
 developers agree that you should gain commit privileges you are then extended
 an official offer.
 
+What it Means
+-------------
+
+As contributors to the CPython project, our shared responsibility is to
+collaborate constructively with other contributors, including core developers.
+This responsibility covers all forms of contribution, whether that's submitting
+patches to the implementation or documentation, reviewing other peoples'
+patches, triaging issues on the issue tracker, or discussing design and
+development ideas on the core mailing lists.
+
+Core developers accept key additional responsibilities around the ongoing
+management of the project:
+
+* core developers bear the additional responsibility of handling the
+  consequences of accepting a change into the code base or documentation.
+  That includes reverting or fixing it if it causes problems in the
+  Buildbot fleet or someone spots a problem in post-commit review, as well
+  as helping out the release manager in resolving any problems found during
+  the pre-release testing cycle. While all contributors are free to help out
+  with this part of the process, and it is most welcome when they do, the
+  actual responsibility rests with the core developer that merged the change
+* core developers also bear the primary responsibility for deciding when
+  changes proposed on the issue tracker should be escalated to python-ideas
+  or python-dev for wider discussion, as well as suggesting the use of the
+  Python Enhancement Proposal process to manage the design and justifcation
+  of complex changes, or changes with a potentially significant impact on
+  end users
+
+As a result of the additional responsibilities they accept, core developers
+gain the privilege of being able to approve proposed changes, as well as being
+able to reject them as inappropriate. Core developers are also able to request
+that even already merged changes be escalated to python-dev for further
+discussion, and potentially even reverted prior to release.
+
+Becoming a core developer isn't a binary "all-or-nothing" status - CPython
+is a large project, and different core developers accept responsibility for
+making design and development decisions in different areas (as documented
+in the :ref:`experts` and :ref:`developers`).
 
 Gaining Commit Privileges
 -------------------------
