Document the Docserv config migration process (#250)

Add a new section into the Developer Guide about how to migrate the
old Docserv config (version 6) into new Portal config (version 7).


---------

Co-authored-by: Sushant Gaurav <[email protected]>

Author: tomschr

changelog.d/250.doc.rst

@@ -0,0 +1,2 @@
+Add a new topic into the Developer Guide about how to migrate the
+old Docserv config (version 6) into new Portal config (version 7).

docs/source/developer/index.rst

@@ -29,6 +29,7 @@ This guide provides all the necessary information for contributing to the projec
    create-release
    trigger-actions
 
+   migrate-config
    build-docs
    howto
 

docs/source/developer/migrate-config.rst

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+.. _migrate-config:
+
+Migrating old Docserv Config to new Portal Config
+=================================================
+
+.. note::
+
+   This section is used to document the migration process from the old Docserv config to the new Portal Schema. It has to be done only once and is not
+   relevant for the regular users of the new Portal Schema or users starting
+   from scratch.
+
+With the introduction of the new Portal Schema in version 7, the schema got
+a massive overhaul.
+
+Therefore, the old Docserv config is not compatible with the new Portal Schema
+anymore and needs to be migrated. The migration process can be done by a
+migration XSLT stylesheet.
+
+You have two options how the result can look like:
+
+* A directory with multiple files.
+
+  This is the recommended approach if you want to organize your configuration
+  in a modular way and split the configuration into multiple files.
+  It allows for better tracking of changes and easier collaboration.
+  Files are referenced by XInclude elements and resolved during the validation
+  process.
+
+* A single configuration file.
+
+  This is useful if you want to debug the whole file, want to search for
+  specific entries or values, or just prefer a single file.
+
+
+.. _migration-prerequisites:
+
+Pre-requisites
+--------------
+
+Before starting the migration process, ensure you have the following tools installed:
+
+* :command:`xmllint`
+* :command:`xsltproc`
+* :command:`jing`
+
+Furthermore, you need a Docserv stitchfile:
+
+* Copy it with :command:`scp` from the Docserv server to your local machine.
+
+  The Docserv stitchfile, typically located at
+  :file:`/tmp/docserv-stitch-${{DATE}}.xml` (whereas ``${DATE}`` is the
+  ISO date of the stitchfile creation in the YYYY-MM-DD format).
+
+* Create it locally by following the instructions in :ref:`prepare-stitchfile`.
+
+
+
+.. _prepare-stitchfile:
+
+Preparing the Docserv Stitchfile
+--------------------------------
+
+.. note::
+
+   The steps below is what the command :command:`docserv-stitch` does on
+   the Docserv server to create the stitchfile. Of course, the script is
+   more complex and takes care of validation and other checks, but the above steps are the core of the stitchfile creation process.
+
+   As such, make sure your Docserv configs are valid.
+
+
+If you don't have access to the Docserv server or prefer to create the stitchfile locally, follow these steps to prepare it:
+
+#. Clone the Docserv config repo if you haven't already:
+
+   .. code-block:: console
+
+      git clone https://gitlab.suse.de/susedoc/docserv-config.git
+      cd docserv-config/config.d
+
+#. Set the result file name and path:
+
+   .. code-block:: console
+
+      stitchfile="/tmp/docserv-stitch-$(date --iso-8601).xml"
+
+#. Prepare the header of the stitchfile:
+
+   .. code-block:: console
+
+      cat << EOF > "$stitchfile"
+      <?xml version="1.0" encoding="UTF-8"?>
+      <docservconfig>
+      <!-- <hashes>...</hashes> -->
+
+      EOF
+
+#. Copy content from all categories into result:
+
+   .. code-block:: console
+
+      xmllint --xpath "/*" _categories.xml >> "$stitchfile"
+
+#. Append all config files to the result:
+
+   .. code-block:: console
+
+      xmllint --xpath "/*" [a-z]*.xml >> "$stitchfile"
+
+#. Close the root element:
+
+   .. code-block:: console
+
+      printf "</docservconfig>\n" >> "$stitchfile"
+
+
+.. _convert-stitchfile:
+
+Converting the Stitchfile
+-------------------------
+
+To convert the stitchfile to the new Portal Schema format, use:
+
+* the command :command:`xsltproc` to run the XSLT transformation,
+* some of the available XSLT parameters to customize the output as needed (see :ref:`available-xslt-parameters`),
+* the migration XSLT stylesheet located at :file:`src/docbuild/config/xml/data/convert-v6-to-v7.xsl`, and
+* the stitchfile you prepared in the :ref:`previous section <prepare-stitchfile>`.
+
+
+.. _available-xslt-parameters:
+
+Available XSLT Parameters
+~~~~~~~~~~~~~~~~~~~~~~~~~
+
+The migration XSLT stylesheet accepts the following XSLT parameters:
+
+* ``cat.prefix`` (default ``cat.``)
+
+  The prefix for category IDs.
+
+* ``schemafile`` (default empty)
+
+  The path to the new Portal Schema file (e.g., :file:`portal-config.rnc`).
+  The stylesheet recognize the format (RNC or RNG) and changes the ``<?xml-model?>`` PI accordingly.
+
+* ``outputfile`` (default :file:`portal.xml`)
+
+  The name of the main configuration file.
+
+* ``outputdir`` (default :file:`output/`)
+
+  The base directory where the output file(s) will be saved.
+  If you want to use the current directory, use ``./``.
+
+* ``use.xincludes`` (default ``false``)
+
+  A boolean parameter that determines whether to use XInclude elements in the output.
+  Set it to ``true`` to create a directory with multiple files, or use the
+  default to create a single configuration file.
+
+* ``schemaversion`` (default latest)
+
+  The version of the new Portal Schema to target. This is used to determine the necessary transformations to apply during the migration process.
+
+
+.. _create-config-file-with-multiple-files:
+
+Creating Multiple Files
+~~~~~~~~~~~~~~~~~~~~~~~
+
+To create a directory with multiple files, do the following:
+
+#. Run the XSLT transformation with the following command:
+
+   .. code-block:: console
+
+      xsltproc --stringparam outputfile portal.xml \
+        --stringparam outputdir "./output/" \
+        --param use.xincludes 'true()' \
+        src/docbuild/config/xml/data/convert-v6-to-v7.xsl $stitchfile
+
+   This will create all files in the :file:`output/` directory, with the main
+   configuration file named :file:`portal.xml` and additional files for
+   each category as needed.
+
+#. Copy the generated files to the desired location.
+
+#. Adjust the env configuration to point to the main configuration file,
+   use the variable :literal:`paths.config_dir` and :literal:`paths.main_portal_config`.
+
+
+.. _create-single-config-file:
+
+Creating a Single File
+~~~~~~~~~~~~~~~~~~~~~~
+
+To create a single configuration file, , do the following:
+
+#. Run the XSLT transformation with the following command:
+
+   .. code-block:: console
+
+      xsltproc --stringparam schemafile "portal-config.rnc" \
+        --stringparam outputfile portal-$(date --iso-8601).xml \
+        --stringparam outputdir "./" \
+        src/docbuild/config/xml/data/convert-v6-to-v7.xsl $stitchfile
+
+   This will create a file named :file:`portal-<DATE>.xml` in the current directory.
+
+#. Copy the generated output file to the desired location.
+
+#. Adjust the env configuration to point to the main configuration file,
+   use the variable :literal:`paths.config_dir` and :literal:`paths.main_portal_config`.