Build source type images by default

Source images get the most test coverage, so it makes sense to build
these by default.

Change-Id: Ie10a41a94af95075a1b91feb2b74ade02b17117e

doc/source/admin/image-building.rst

@@ -118,11 +118,11 @@ When building images, there are two methods of the OpenStack install. One is
 ``binary``. Another is ``source``. The ``binary`` means that OpenStack will be
 installed from apt/dnf. And the ``source`` means that OpenStack will be
 installed from upstream sources. The default method of the OpenStack install is
-``binary``. It can be changed to ``source`` using the ``-t`` option:
+``source``. It can be changed to ``binary`` using the ``-t`` option:
 
 .. code-block:: console
 
-   kolla-build -t source
+   kolla-build -t binary
 
 The locations of OpenStack source code are written in ``kolla-build.conf``.
 The source type supports ``url``, ``git``, and ``local``. The location of

kolla/common/config.py

@@ -203,7 +203,7 @@ _CLI_OPTS = [
                help='Format to write the final results in'),
     cfg.StrOpt('tarballs-base', default=TARBALLS_BASE,
                help='Base url to OpenStack tarballs'),
-    cfg.StrOpt('type', short='t', default='binary',
+    cfg.StrOpt('type', short='t', default='source',
                choices=INSTALL_TYPE_CHOICES,
                dest='install_type',
                help=('The method of the OpenStack install.')),

releasenotes/notes/default-type-source-f0c5cf1d97e2f345.yaml

@@ -0,0 +1,8 @@
+---
+upgrade:
+  - |
+    Updates the default image type to ``source``. Users wishing to build
+    ``binary`` type images should either specify the ``--type binary`` CLI
+    argument or set ``[DEFAULT] type=binary`` in ``kolla-build.conf``.
+    This change is to reflect the reality that source images are tested more
+    thoroughly and we (as OpenStack community) have better control over them.