docs: Add LTS releases section and 52 what's new page

Let's create a section to have the 'what's new' between LTSs and
add the next known LTS page there.
Signed-off-by: NAmador Pahim <apahim@redhat.com>

docs/source/release_notes/index.rst

@@ -6,6 +6,13 @@ Release Notes
 
 The following pages summarize what is new in Avocado:
 
+Regular Releases
+================
+
+The regular releases are released after each sprint, which usually takes
+3 weeks. Regular releases are supported only until the next version is
+released.
+
 .. toctree::
    :maxdepth: 1
 
@@ -37,3 +44,17 @@ The following pages summarize what is new in Avocado:
    0_27_0
    0_26_0
    0_25_0
+
+Long Term Stability Releases
+============================
+
+The LTS releases are regular releases considering the release cycle, but
+a new branch is created and bugfixes are backported on demand for a
+period of about 18 months after the release. Every year (or so) a new
+LTS version is released. Two subsequent LTS versions are guaranteed to
+have 6 months of supportability overlap.
+
+.. toctree::
+   :maxdepth: 1
+
+   lts/52_0

docs/source/release_notes/lts/52_0.rst

+========
+52.0 LTS
+========
+
+The Avocado team is proud to present another release: Avocado version
+52.0, the second Avocado LTS version.
+
+What's new?
+===========
+
+When compared to the last LTS (v36), the main changes introduced by this
+versions are:
+
+- Support for TAP[2] version 12 results, which are generated by default
+  in test results directory (``results.tap`` file).
+- The download of assets in tests now allow for an expiration time.
+- Environment variables can be propagated into tests running on remote
+  systems.
+- The plugin interfaces have been moved into the
+  ``avocado.core.plugin_interfaces`` module.
+- Support for running tests in a Docker container.
+- Introduction of the "Fail Fast" feature (``--failfast on`` option) to
+  the ``run`` command, which interrupts the Job on a first test failure.
+- Special keyword ``latest`` for replaying previous jobs.
+- Support to replay a Job by path (in addition to the Job ID method and
+  the ``latest`` keyword).
+- Diff-like categorized report of jobs
+  (``avocado diff <JOB_1> <JOB_2>``).
+- The introduction of a ``rr`` based wrapper.
+- The automatic VM IP detection that kicks in when one uses
+  ``--vm-domain`` without a matching ``--vm-hostname``, now uses a more
+  reliable method (libvirt/qemu-gust-agent query).
+- Set ``LC_ALL=C`` by default on sysinfo collection to simplify avocado
+  diff comparison between different machines.
+- Result plugins system is now pluggable and the results plugins (JSON,
+  XUnit, HTML) were turned into stevedore plugins. They are now listed
+  in the ``avocado plugins`` command.
+- Multiplexer was replaced with Varianter plugging system with defined
+  API to register plugins that generate test variants.
+- Old ``--multiplex`` argument, which used to turn yaml files into
+  variants, is now handled by an optional plugin called ``yaml_to_mux``
+  and the ``--multiplex`` option is being deprecated in favour of
+  the ``--mux-yaml`` option, which behaves the same way.
+- It’s now possible to disable plugins by using the configuration file.
+- Better error handling of the virtual machine plugin (``--vm-domain``
+  and related options).
+- When discovering tests on a directory, the result now is a properly
+  alphabetically ordered list of tests.
+- Plugins can now be setup in Avocado configuration file to run at a
+  specific order.
+- Support for filtering tests by user supplied "tags".
+- Users can now see the test tags when listing tests with the ``-V``
+  (verbose) option.
+- Users can now choose to keep the complete set of files, including
+  temporary ones, created during an Avocado job run by using the
+  ``--keep-tmp`` option (e.g. to keep those files for ``rr``).
+- Tests running with the external runner (``--external-runner``) feature
+  will now have access to the extended behavior for SIMPLE tests, such
+  as being able to exit a test with the WARNING status.
+- Encoding support was improved and now Avocado should safely treat
+  localized test-names.
+- Test writers now have access to a test temporary directory that will
+  last not only for the duration of the test, but for the duration of
+  the whole job execution to allow sharing state/exchanging data between
+  tests. The path for that directory is available via Test API
+  (``self.teststmpdir``) and via environment variable
+  (``AVOCADO_TESTS_COMMON_TMPDIR``).
+- Avocado is now available on Fedora standard repository. The package
+  name is ``python2-avocado``. The optional plugins and examples
+  packages are also available. Run ``dnf search avocado`` to list them
+  all.
+- Optional plugins and examples packages are also available on PyPI
+  under ``avocado-framework`` name.
+- Avocado test writers can now use a family of decorators, namely
+  ``avocado.skip()``, ``avocado.skipIf()`` and ``avocado.skipUnless()``
+  to skip the execution of tests.
+- Sysinfo collection based on command execution now allows a timeout to
+  be set in the Avocado configuration file.
+- The non-local runner plugins, the html plugin and the yaml_to_mux
+  plugin are now distributed in separate packages.
+- The Avocado main process will now try to kill all test processes
+  before terminating itself when it receives a SIGTERM.
+- Support for new type of test status, ``CANCEL``, and of course the
+  mechanisms to set a test with this status (e.g. via ``self.cancel()``).
+- ``avocado.TestFail``, ``avocado.TestError`` and ``avocado.TestCancel``
+  are now public Avocado Test APIs, available in the main `avocado`
+  namespace.
+- Introduction of the robot plugin, which allows Robot Framework tests
+  to be listed and executed natively within Avocado.
+- A brand new ResultsDB optional plugin.
+- Listing of supported loaders (``--loaders \?``) was refined.
+- Variant-IDs generated by yaml_to_mux plugin now include leaf node
+  names to make them more meaningful, making easier to skim through
+  the results.
+- `yaml_to_mux` now supports internal filters defined inside the YAML
+  file expanding the filtering capabilities even further.
+- Avocado now supports resuming jobs that were interrupted.
+- The HTML report now presents the test ID and variant ID in separate
+  columns, allowing users to also sort and filter results based on those
+  specific fields.
+- The HTML report will now show the test parameters used in a test when
+  the user hovers the cursor over the test name.
+- Avocado now reports the total job execution time on the UI, instead of
+  just the tests execution time.
+- New ``avocado variants`` has been added which supersedes the
+  ``avocado multiplex``.
+- Loaders were tweaked to provide more info on ``avocado list -V``
+  especially when they don't recognize the reference.
+- Users can use ``--ignore-missing-references on`` to run a job with
+  undiscovered test references
+- Users can now choose in which order the job will execute tests (from
+  its suite) and variants. The two available options are
+  ``--execution-order=variants-per-test`` (default) or
+  ``--execution-order=tests-per-variant``.
+- Test methods can be recursively discovered from parent classes by upon
+  the ``:avocado: recursive`` docstring directive.
+
+Besides the list above, we had several improvements in our ``utils``
+libraries that are important for test writers, some of them are listed
+below:
+
+- ``time_to_seconds``, ``geometric_mean`` and ``compare_matrices`` were
+  added in ``avocado.utils.data_structures``.
+- ``avocado.utils.distro`` was refined.
+- Many ``avocado.utils`` new modules were introduced, like ``filelock``,
+  ``lv_utils``, ``multipath``, ``partition`` and ``pci``.
+- ``avocado.utils.memory`` contains several new methods.
+- New ``avocado.utils.process.SubProcess.get_pid()`` method.
+- ``sudo`` support in ``avocado.utils.process`` was improved
+- The ``avocado.utils.process`` library makes it possible to ignore
+  spawned background processes.
+- New ``avocado.utils.linux_modules.check_kernel_config()``.
+- Users of the ``avocado.utils.process`` module will now be able to access
+  the process ID in the ``avocado.utils.process.CmdResult``.
+- Improved ``avocado.utils.iso9660`` with a more complete standard API
+  across all back-end implementations.
+- Improved ``avocado.utils.build.make()``, which will now return the make
+  process exit status code.
+- The ``avocado.Test`` class now better exports (and protects) the core
+  class attributes members (such as ``params`` and ``runner_queue``).
+- ``avocado.utils.linux_modules`` functions now returns module name,
+  size, submodules if present, filename, version, number of modules
+  using it, list of modules it is dependent on and finally a list of
+  ``params``.
+
+It is also worth mentioning:
+
+- Improved documentation, with new sections to Release Notes and
+  Optional Plugins, very improved Contribution and Community Guide. New
+  content and new examples everywhere.
+- The avocado-framework-tests GitHub organization was founded to
+  encourage companies to share Avocado tests.
+- Bugs were always handled as high priority and every single version was
+  delivered with all the reported bugs properly fixed.
+
+When compared to the last LTS, we had:
+
+- 1187 commits (and counting).
+- 15 new versions.
+- 4811 more lines of Python code (+27,42%).
+- 1800 more lines of code comment (+24,67%).
+- 31 more Python files (+16,48%).
+- 69 closed GitHub issues.
+- 34 contributors from at least 12 different companies, 26 of them
+  contributing for the fist time to the project.