Add documentation about development infrastructure

Resolves Exawind#1105

docs/source/developer/index.rst

@@ -11,3 +11,4 @@ Developer Manual
    Developer Workflow Best Practices <workflow.rst>
    Code Style Guide <style.rst>
    Contributing <contrib.rst>
+   Project Development Infrastructure <infra.rst>

docs/source/developer/infra.rst

@@ -0,0 +1,42 @@
+Development Infrastructure
+==========================
+
+This document describes the development infrastructure used by the nalu-wind project.
+
+Docker Container
+----------------
+
+The docker container `ecpe4s/exawind-snapshot <https://hub.docker.com/r/ecpe4s/exawind-snapshot>`_
+is build by an external collaborator in the E4S project.
+Its definition is at https://gitlab.e4s.io/uo-public/exawind-snapshot.
+
+It is based on an Ubuntu with GCC on which spack-manager is used to install exawind+hypre+openfast.
+
+It is build and pushed to Dockerhub daily.
+
+Continuous Integration
+----------------------
+
+There are currently two different systems the continuously check the code of this project.
+
+GitHub Actions
+^^^^^^^^^^^^^^
+
+The `github actions workflow <https://github.com/Exawind/nalu-wind/blob/master/.github/workflows/ci.yml>`_
+runs on every pull request towards master as well as all commits on master.
+
+It does the following things:
+
+* Style Check of the CPP code using clang-format with clang version 13
+* Run the unit tests
+
+    * Uses the docker container to allow to reuse the third party libraries
+    * Rebuilds nalu-wind with the source from the commit on which the ci is run
+    * Run all test with `unit` in the label using ctest
+
+Daily Regression Tests
+^^^^^^^^^^^^^^^^^^^^^^
+
+Additionally, the project is tested more extensively on some machines at NREL.
+The results are collected at `CDash <https://my.cdash.org/index.php?project=Exawind>`_.
+For more info see :ref:`ref-testing-cdash`.

docs/source/developer/testing.rst

@@ -115,6 +115,8 @@ created. Also, if you are using a mesh file that doesn't exist in the mesh repo,
 update the submodule in the Nalu-Wind main repo to use the latest commit of the mesh submodule repo.
 
 
+.. _ref-testing-cdash:
+
 Adding Testing Machines to CDash
 --------------------------------