DOC: update contributing.rst for ci (#15880)

* DOC: update contributing.rst for ci

* typos & auto-cancel links

* make it a note

* add back accid deleted section

Author: jreback

doc/source/_static/ci.png

@@ -113,13 +113,6 @@ want to clone your fork to your machine::
 This creates the directory `pandas-yourname` and connects your repository to
 the upstream (main project) *pandas* repository.
 
-The testing suite will run automatically on Travis-CI and Appveyor once your
-pull request is submitted.  However, if you wish to run the test suite on a
-branch prior to submitting the pull request, then Travis-CI and/or AppVeyor
-need to be hooked up to your GitHub repository.  Instructions for doing so
-are `here <http://about.travis-ci.org/docs/user/getting-started/>`__ for
-Travis-CI and `here <https://www.appveyor.com/docs/>`__ for AppVeyor.
-
 Creating a branch
 -----------------
 
@@ -432,7 +425,8 @@ Building master branch documentation
 
 When pull requests are merged into the *pandas* ``master`` branch, the main parts of
 the documentation are also built by Travis-CI. These docs are then hosted `here
-<http://pandas-docs.github.io/pandas-docs-travis>`__.
+<http://pandas-docs.github.io/pandas-docs-travis>`__, see also
+the :ref:`Continuous Integration <contributing.ci>` section.
 
 Contributing to the code base
 =============================
@@ -444,8 +438,9 @@ Code standards
 --------------
 
 Writing good code is not just about what you write. It is also about *how* you
-write it. During testing on Travis-CI, several tools will be run to check your
-code for stylistic errors. Generating any warnings will cause the test to fail.
+write it. During :ref:`Continuous Integration <contributing.ci>` testing, several
+tools will be run to check your code for stylistic errors.
+Generating any warnings will cause the test to fail.
 Thus, good style is a requirement for submitting code to *pandas*.
 
 In addition, because a lot of people use our library, it is important that we
@@ -467,7 +462,8 @@ Here are *some* of the more common ``cpplint`` issues:
   - we restrict line-length to 80 characters to promote readability
   - every header file must include a header guard to avoid name collisions if re-included
 
-Travis-CI will run the `cpplint <https://pypi.python.org/pypi/cpplint>`_ tool
+:ref:`Continuous Integration <contributing.ci>`. will run the
+`cpplint <https://pypi.python.org/pypi/cpplint>`_ tool
 and report any stylistic errors in your code. Therefore, it is helpful before
 submitting code to run the check yourself::
 
@@ -514,7 +510,8 @@ the more common ``PEP8`` issues:
   - we restrict line-length to 79 characters to promote readability
   - passing arguments should have spaces after commas, e.g. ``foo(arg1, arg2, kw1='bar')``
 
-Travis-CI will run the `flake8 <http://pypi.python.org/pypi/flake8>`_ tool
+:ref:`Continuous Integration <contributing.ci>` will run
+the `flake8 <http://pypi.python.org/pypi/flake8>`_ tool
 and report any stylistic errors in your code. Therefore, it is helpful before
 submitting code to run the check yourself on the diff::
 
@@ -542,6 +539,35 @@ existing code, so don't break it if at all possible.  If you think breakage is r
 clearly state why as part of the pull request.  Also, be careful when changing method
 signatures and add deprecation warnings where needed.
 
+.. _contributing.ci:
+
+Testing Thru Continuous Integration
+-----------------------------------
+
+The pandas testing suite will run automatically on Travis-CI, Appveyor, and Circle CI
+continuous integration services, once your pull request is submitted.
+However, if you wish to run the test suite on a branch prior to submitting the pull request,
+then Travis-CI, Appveyor and/or CircleCI need to be hooked up to your GitHub repository.
+Instructions for doing so are `here <http://about.travis-ci.org/docs/user/getting-started/>`__ for
+Travis-CI, `here <https://www.appveyor.com/docs/>`__ for Appveyor, and
+`here <https://circleci.com/>`__ for CircleCI.
+
+A pull-request will be considered for merging when you have an all 'green' build. See
+this example.
+
+.. image:: _static/ci.png
+
+
+.. note::
+
+   Pushing to *your* branch will cancel any non-currently-running tests for that
+   same pull-request for Appveyor. For Travis CI, you can enable the auto-cancel feature
+   `here <https://docs.travis-ci.com/user/customizing-the-build/#Building-only-the-latest-commit>`__ and
+   for CircleCI `here <https://circleci.com/changelog-legacy/#option-to-auto-cancel-redundant-builds>`__.
+
+.. _contributing.tdd:
+
+
 Test-driven development/code writing
 ------------------------------------
 
@@ -875,12 +901,8 @@ updated.  Pushing them to GitHub again is done by::
     git push -f origin shiny-new-feature
 
 This will automatically update your pull request with the latest code and restart the
-Travis-CI tests.
+:ref:`Continuous Integration <contributing.ci>` tests.
 
-If your pull request is related to the ``pandas.io.gbq`` module, please see
-the section on :ref:`Running Google BigQuery Integration Tests
-<contributing.gbq_integration_tests>` to configure a Google BigQuery service
-account for your pull request on Travis-CI.
 
 Delete your merged branch (optional)
 ------------------------------------