ref-manual: move migration guides to separate document

This makes the reference manual much lighter by moving
the migration guides to a separate document.

The migration guides are also reordered from last to first,
and they appear directly in the left bar, making them easier
to find in the documentation.

(From yocto-docs rev: 5121b86ee97eb62a0c69c9ad1fc0e3fabbe3e934)

Signed-off-by: Michael Opdenacker <michael.opdenacker@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 308 insertions, 0 deletions

diff --git a/documentation/migration-guides/migration-2.5.rst b/documentation/migration-guides/migration-2.5.rst
new file mode 100644
index 0000000000..c7e0760463
--- /dev/null
+++ b/documentation/migration-guides/migration-2.5.rst
@@ -0,0 +1,308 @@
+Release 2.5 (sumo)
+==================
+
+This section provides migration information for moving to the Yocto
+Project 2.5 Release (codename "sumo") from the prior release.
+
+.. _migration-2.5-packaging-changes:
+
+Packaging Changes
+-----------------
+
+This section provides information about packaging changes that have
+occurred:
+
+-  ``bind-libs``: The libraries packaged by the bind recipe are in a
+   separate ``bind-libs`` package.
+
+-  ``libfm-gtk``: The ``libfm`` GTK+ bindings are split into a
+   separate ``libfm-gtk`` package.
+
+-  ``flex-libfl``: The flex recipe splits out libfl into a separate
+   ``flex-libfl`` package to avoid too many dependencies being pulled in
+   where only the library is needed.
+
+-  ``grub-efi``: The ``grub-efi`` configuration is split into a
+   separate ``grub-bootconf`` recipe. However, the dependency
+   relationship from ``grub-efi`` is through a virtual/grub-bootconf
+   provider making it possible to have your own recipe provide the
+   dependency. Alternatively, you can use a BitBake append file to bring
+   the configuration back into the ``grub-efi`` recipe.
+
+-  *armv7a Legacy Package Feed Support:* Legacy support is removed for
+   transitioning from ``armv7a`` to ``armv7a-vfp-neon`` in package
+   feeds, which was previously enabled by setting
+   ``PKGARCHCOMPAT_ARMV7A``. This transition occurred in 2011 and active
+   package feeds should by now be updated to the new naming.
+
+.. _migration-2.5-removed-recipes:
+
+Removed Recipes
+---------------
+
+The following recipes have been removed:
+
+-  ``gcc``: The version 6.4 recipes are replaced by 7.x.
+
+-  ``gst-player``: Renamed to ``gst-examples`` as per upstream.
+
+-  ``hostap-utils``: This software package is obsolete.
+
+-  ``latencytop``: This recipe is no longer maintained upstream. The
+   last release was in 2009.
+
+-  ``libpfm4``: The only file that requires this recipe is
+   ``oprofile``, which has been removed.
+
+-  ``linux-yocto``: The version 4.4, 4.9, and 4.10 recipes have been
+   removed. Versions 4.12, 4.14, and 4.15 remain.
+
+-  ``man``: This recipe has been replaced by modern ``man-db``
+
+-  ``mkelfimage``: This tool has been removed in the upstream coreboot
+   project, and is no longer needed with the removal of the ELF image
+   type.
+
+-  ``nativesdk-postinst-intercept``: This recipe is not maintained.
+
+-  ``neon``: This software package is no longer maintained upstream
+   and is no longer needed by anything in OpenEmbedded-Core.
+
+-  ``oprofile``: The functionality of this recipe is replaced by
+   ``perf`` and keeping compatibility on an ongoing basis with ``musl``
+   is difficult.
+
+-  ``pax``: This software package is obsolete.
+
+-  ``stat``: This software package is not maintained upstream.
+   ``coreutils`` provides a modern stat binary.
+
+-  ``zisofs-tools-native``: This recipe is no longer needed because
+   the compressed ISO image feature has been removed.
+
+.. _migration-2.5-scripts-and-tools-changes:
+
+Scripts and Tools Changes
+-------------------------
+
+The following are changes to scripts and tools:
+
+-  ``yocto-bsp``, ``yocto-kernel``, and ``yocto-layer``: The
+   ``yocto-bsp``, ``yocto-kernel``, and ``yocto-layer`` scripts
+   previously shipped with poky but not in OpenEmbedded-Core have been
+   removed. These scripts are not maintained and are outdated. In many
+   cases, they are also limited in scope. The
+   ``bitbake-layers create-layer`` command is a direct replacement for
+   ``yocto-layer``. See the documentation to create a BSP or kernel
+   recipe in the ":ref:`bsp-guide/bsp:bsp kernel recipe example`" section.
+
+-  ``devtool finish``: ``devtool finish`` now exits with an error if
+   there are uncommitted changes or a rebase/am in progress in the
+   recipe's source repository. If this error occurs, there might be
+   uncommitted changes that will not be included in updates to the
+   patches applied by the recipe. A -f/--force option is provided for
+   situations that the uncommitted changes are inconsequential and you
+   want to proceed regardless.
+
+-  ``scripts/oe-setup-rpmrepo`` script: The functionality of
+   ``scripts/oe-setup-rpmrepo`` is replaced by
+   ``bitbake package-index``.
+
+-  ``scripts/test-dependencies.sh`` script: The script is largely made
+   obsolete by the recipe-specific sysroots functionality introduced in
+   the previous release.
+
+.. _migration-2.5-bitbake-changes:
+
+BitBake Changes
+---------------
+
+The following are BitBake changes:
+
+-  The ``--runall`` option has changed. There are two different
+   behaviors people might want:
+
+   -  *Behavior A:* For a given target (or set of targets) look through
+      the task graph and run task X only if it is present and will be
+      built.
+
+   -  *Behavior B:* For a given target (or set of targets) look through
+      the task graph and run task X if any recipe in the taskgraph has
+      such a target, even if it is not in the original task graph.
+
+   The ``--runall`` option now performs "Behavior B". Previously
+   ``--runall`` behaved like "Behavior A". A ``--runonly`` option has
+   been added to retain the ability to perform "Behavior A".
+
+-  Several explicit "run this task for all recipes in the dependency
+   tree" tasks have been removed (e.g. ``fetchall``, ``checkuriall``,
+   and the ``*all`` tasks provided by the ``distrodata`` and
+   ``archiver`` classes). There is a BitBake option to complete this for
+   any arbitrary task. For example::
+
+      bitbake <target> -c fetchall
+
+   should now be replaced with::
+
+      bitbake <target> --runall=fetch
+
+.. _migration-2.5-python-and-python3-changes:
+
+Python and Python 3 Changes
+---------------------------
+
+The following are auto-packaging changes to Python and Python 3:
+
+The script-managed ``python-*-manifest.inc`` files that were previously
+used to generate Python and Python 3 packages have been replaced with a
+JSON-based file that is easier to read and maintain. A new task is
+available for maintainers of the Python recipes to update the JSON file
+when upgrading to new Python versions. You can now edit the file
+directly instead of having to edit a script and run it to update the
+file.
+
+One particular change to note is that the Python recipes no longer have
+build-time provides for their packages. This assumes ``python-foo`` is
+one of the packages provided by the Python recipe. You can no longer run
+``bitbake python-foo`` or have a
+:term:`DEPENDS` on ``python-foo``,
+but doing either of the following causes the package to work as
+expected::
+
+   IMAGE_INSTALL_append = " python-foo"
+
+or ::
+
+   RDEPENDS_${PN} = "python-foo"
+
+The earlier build-time provides behavior was a quirk of the
+way the Python manifest file was created. For more information on this
+change please see :yocto_git:`this commit
+</poky/commit/?id=8d94b9db221d1def42f091b991903faa2d1651ce>`.
+
+.. _migration-2.5-miscellaneous-changes:
+
+Miscellaneous Changes
+---------------------
+
+The following are additional changes:
+
+-  The ``kernel`` class supports building packages for multiple kernels.
+   If your kernel recipe or ``.bbappend`` file mentions packaging at
+   all, you should replace references to the kernel in package names
+   with ``${KERNEL_PACKAGE_NAME}``. For example, if you disable
+   automatic installation of the kernel image using
+   ``RDEPENDS_kernel-base = ""`` you can avoid warnings using
+   ``RDEPENDS_${KERNEL_PACKAGE_NAME}-base = ""`` instead.
+
+-  The ``buildhistory`` class commits changes to the repository by
+   default so you no longer need to set ``BUILDHISTORY_COMMIT = "1"``.
+   If you want to disable commits you need to set
+   ``BUILDHISTORY_COMMIT = "0"`` in your configuration.
+
+-  The ``beaglebone`` reference machine has been renamed to
+   ``beaglebone-yocto``. The ``beaglebone-yocto`` BSP is a reference
+   implementation using only mainline components available in
+   OpenEmbedded-Core and ``meta-yocto-bsp``, whereas Texas Instruments
+   maintains a full-featured BSP in the ``meta-ti`` layer. This rename
+   avoids the previous name clash that existed between the two BSPs.
+
+-  The ``update-alternatives`` class no longer works with SysV ``init``
+   scripts because this usage has been problematic. Also, the
+   ``sysklogd`` recipe no longer uses ``update-alternatives`` because it
+   is incompatible with other implementations.
+
+-  By default, the :ref:`cmake <ref-classes-cmake>` class uses
+   ``ninja`` instead of ``make`` for building. This improves build
+   performance. If a recipe is broken with ``ninja``, then the recipe
+   can set ``OECMAKE_GENERATOR = "Unix Makefiles"`` to change back to
+   ``make``.
+
+-  The previously deprecated ``base_*`` functions have been removed in
+   favor of their replacements in ``meta/lib/oe`` and
+   ``bitbake/lib/bb``. These are typically used from recipes and
+   classes. Any references to the old functions must be updated. The
+   following table shows the removed functions and their replacements:
+
+   +------------------------------+----------------------------------------------------------+
+   | *Removed*                    | *Replacement*                                            |
+   +==============================+==========================================================+
+   | base_path_join()             | oe.path.join()                                           |
+   +------------------------------+----------------------------------------------------------+
+   | base_path_relative()         | oe.path.relative()                                       |
+   +------------------------------+----------------------------------------------------------+
+   | base_path_out()              | oe.path.format_display()                                 |
+   +------------------------------+----------------------------------------------------------+
+   | base_read_file()             | oe.utils.read_file()                                     |
+   +------------------------------+----------------------------------------------------------+
+   | base_ifelse()                | oe.utils.ifelse()                                        |
+   +------------------------------+----------------------------------------------------------+
+   | base_conditional()           | oe.utils.conditional()                                   |
+   +------------------------------+----------------------------------------------------------+
+   | base_less_or_equal()         | oe.utils.less_or_equal()                                 |
+   +------------------------------+----------------------------------------------------------+
+   | base_version_less_or_equal() | oe.utils.version_less_or_equal()                         |
+   +------------------------------+----------------------------------------------------------+
+   | base_contains()              | bb.utils.contains()                                      |
+   +------------------------------+----------------------------------------------------------+
+   | base_both_contain()          | oe.utils.both_contain()                                  |
+   +------------------------------+----------------------------------------------------------+
+   | base_prune_suffix()          | oe.utils.prune_suffix()                                  |
+   +------------------------------+----------------------------------------------------------+
+   | oe_filter()                  | oe.utils.str_filter()                                    |
+   +------------------------------+----------------------------------------------------------+
+   | oe_filter_out()              | oe.utils.str_filter_out() (or use the \_remove operator) |
+   +------------------------------+----------------------------------------------------------+
+
+-  Using ``exit 1`` to explicitly defer a postinstall script until first
+   boot is now deprecated since it is not an obvious mechanism and can
+   mask actual errors. If you want to explicitly defer a postinstall to
+   first boot on the target rather than at ``rootfs`` creation time, use
+   ``pkg_postinst_ontarget()`` or call
+   ``postinst_intercept delay_to_first_boot`` from ``pkg_postinst()``.
+   Any failure of a ``pkg_postinst()`` script (including ``exit 1``)
+   will trigger a warning during ``do_rootfs``.
+
+   For more information, see the
+   ":ref:`dev-manual/common-tasks:post-installation scripts`"
+   section in the Yocto Project Development Tasks Manual.
+
+-  The ``elf`` image type has been removed. This image type was removed
+   because the ``mkelfimage`` tool that was required to create it is no
+   longer provided by coreboot upstream and required updating every time
+   ``binutils`` updated.
+
+-  Support for .iso image compression (previously enabled through
+   ``COMPRESSISO = "1"``) has been removed. The userspace tools
+   (``zisofs-tools``) are unmaintained and ``squashfs`` provides better
+   performance and compression. In order to build a live image with
+   squashfs+lz4 compression enabled you should now set
+   ``LIVE_ROOTFS_TYPE = "squashfs-lz4"`` and ensure that ``live`` is in
+   ``IMAGE_FSTYPES``.
+
+-  Recipes with an unconditional dependency on ``libpam`` are only
+   buildable with ``pam`` in ``DISTRO_FEATURES``. If the dependency is
+   truly optional then it is recommended that the dependency be
+   conditional upon ``pam`` being in ``DISTRO_FEATURES``.
+
+-  For EFI-based machines, the bootloader (``grub-efi`` by default) is
+   installed into the image at /boot. Wic can be used to split the
+   bootloader into separate boot and rootfs partitions if necessary.
+
+-  Patches whose context does not match exactly (i.e. where patch
+   reports "fuzz" when applying) will generate a warning. For an example
+   of this see :yocto_git:`this commit
+   </poky/commit/?id=cc97bc08125b63821ce3f616771830f77c456f57>`.
+
+-  Layers are expected to set ``LAYERSERIES_COMPAT_layername`` to match
+   the version(s) of OpenEmbedded-Core they are compatible with. This is
+   specified as codenames using spaces to separate multiple values (e.g.
+   "rocko sumo"). If a layer does not set
+   ``LAYERSERIES_COMPAT_layername``, a warning will is shown. If a layer
+   sets a value that does not include the current version ("sumo" for
+   the 2.5 release), then an error will be produced.
+
+-  The ``TZ`` environment variable is set to "UTC" within the build
+   environment in order to fix reproducibility problems in some recipes.
+
+