doc/user: generate the required package list for the CI distributions

Use yq to extract the package list from the CI configuration, then dump that
into the user docs. This provides the long-requested commands to install all
dependencies without the maintenance effort or risk of going stale.

Note that we are *not* building this in the CI, it's just not needed.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

doc/user/building.rst

@@ -224,6 +224,14 @@ found``.  See
 `this blog post here <https://who-t.blogspot.com/2018/07/meson-fails-with-native-dependency-not-found.html>`_
 for instructions on how to fix it.
 
+..............................................................................
+Build dependencies per distribution
+..............................................................................
+
+
+.. include:: dependencies.rst
+
+
 .. _building_conditional:
 
 ------------------------------------------------------------------------------

doc/user/dependencies.rst

@@ -0,0 +1,21 @@
+.. warning:: The package lists are autogenerated from the `CI <https://gitlab.freedesktop.org/libinput/libinput/-/tree/master/.gitlab-ci.yml>`_.
+
+- Fedora: ::
+
+    dnf install @FEDORA_PACKAGES@
+
+- Ubuntu: ::
+
+    apt install @UBUNTU_PACKAGES@
+
+- Debian: ::
+
+    apt install @DEBIAN_PACKAGES@
+
+- Arch: ::
+
+    pacman -S @ARCH_PACKAGES@
+
+- Alpine: ::
+
+    apk add @ALPINE_PACKAGES@

doc/user/meson.build

@@ -4,6 +4,11 @@ if not sphinx.found()
 	error('Program "sphinx-build" not found or not executable. Try building with -Ddocumentation=false')
 endif
 
+yq = find_program('yq', required : false)
+if not yq.found()
+	warning('Program "yq" not found or not executable. Dependency list will not be built.')
+endif
+
 sphinx_config = configuration_data()
 sphinx_config.set('PROJECT_NAME', meson.project_name())
 sphinx_config.set('PROJECT_VERSION', meson.project_version())
@@ -180,6 +185,19 @@ configure_file(input: 'index.rst',
 	       output: 'index.rst',
 	       configuration: sphinx_config)
 
+dependencies_config = configuration_data()
+if yq.found()
+	distributions = ['fedora', 'ubuntu', 'debian', 'arch', 'alpine']
+	foreach distro : distributions
+		yq_filter = '.distributions[] | select(.name == "@0@") | .packages | join(" ")'.format(distro)
+		deps = run_command(yq, '-r', yq_filter,
+				   join_paths(meson.source_root(), '.gitlab-ci', 'config.yml')).stdout()
+		dependencies_config.set('@0@_PACKAGES'.format(distro.to_upper()), deps)
+endforeach
+endif
+configure_file(input: 'dependencies.rst',
+	       output: 'dependencies.rst',
+	       configuration: dependencies_config)
 
 # do not use -j, it breaks on Ubuntu
 sphinx_output_dir = 'Documentation'