doc/user: add custom 404 pages for the old links

Switching from doxygen to sphinx broke a bunch of links because doxygen used
whatever the argument to @page was - and that usually had underscores. Sphinx
uses filenames (which use dashes) so now we have a bunch of old links going to
a 404. For the transition period at least, insert a custom 404 page for each
of those to tell users this doesn't exist anymore.
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

doc/user/404.rst

+:orphan:
+
+===
+404
+===
+
+This page has permanently moved, probably to `<@TARGET@>`_
+
+This placeholder page will be removed soon.

doc/user/meson.build

@@ -20,6 +20,72 @@ sphinx_conf_py = configure_file(input : 'conf.py.in',
 				configuration : sphinx_config,
 				install : false)
 
+# 404 replacements for old URLs
+# The switch to sphinx caused a few pages to be renamed, sphinx uses
+# filename.html whereas doxygen used whatever the @page foo was. So old docs
+# *mostly* used underscores, now we're consistent with dashes.
+# We can't use htaccess on the server, so let's auto-generate a 404 list
+# with a basic page telling users that the link has moved. This can be
+# removed in a few months, towards the end of 2018.
+#
+# File list is: [current-sphinx-input-file, old-generated-page]
+# If they're the same they'll be ignored.
+src_404s = [
+	[ 'absolute-axes.rst', 'absolute_axes.html'],
+	[ 'absolute-coordinate-ranges.rst', 'absolute_coordinate_ranges.html'],
+	[ 'architecture.rst', 'architecture.html'],
+	[ 'building.rst', 'building_libinput.html'],
+	[ 'button-debouncing.rst', 'button_debouncing.html'],
+	[ 'clickpad-softbuttons.rst', 'clickpad_softbuttons.html'],
+	[ 'configuration.rst', 'config_options.html'],
+	[ 'contributing.rst', 'contributing.html'],
+	[ 'development.rst', 'development.html'],
+	[ 'device-configuration-via-udev.rst', 'udev_config.html'],
+	[ 'device-quirks.rst', 'device-quirks.html'],
+	[ 'faqs.rst', 'faq.html'],
+	[ 'features.rst', 'features.html'],
+	[ 'gestures.rst', 'gestures.html'],
+	[ 'middle-button-emulation.rst', 'middle_button_emulation.html'],
+	[ 'normalization-of-relative-motion.rst', 'motion_normalization.html'],
+	[ 'palm-detection.rst', 'palm_detection.html'],
+	[ 'pointer-acceleration.rst', 'pointer-acceleration.html'],
+	[ 'reporting-bugs.rst', 'reporting_bugs.html'],
+	[ 'scrolling.rst', 'scrolling.html'],
+	[ 'seats.rst', 'seats.html'],
+	[ 'switches.rst', 'switches.html'],
+	[ 't440-support.rst', 't440_support.html'],
+	[ 'tablet-support.rst', 'tablet-support.html'],
+	[ 'tapping.rst', 'tapping.html'],
+	[ 'test-suite.rst', 'test-suite.html'],
+	[ 'timestamps.rst', 'timestamps.html'],
+	[ 'tools.rst', 'tools.html'],
+	[ 'touchpad-jitter.rst', 'touchpad_jitter.html'],
+	[ 'touchpad-jumping-cursors.rst', 'touchpad_jumping_cursor.html'],
+	[ 'touchpad-pressure.rst', 'touchpad_pressure.html'],
+	[ 'touchpads.rst', 'touchpads.html'],
+	[ 'trackpoints.rst', 'trackpoints.html'],
+	[ 'troubleshooting.rst', 'troubleshooting.html'],
+	[ 'what-is-libinput.rst', 'what_is_libinput.html'],
+]
+
+dst_404s = []
+foreach s404 : src_404s
+	target = s404[0]
+	oldpage = s404[1]
+	tname = target.split('.rst')[0]
+	oname = oldpage.split('.html')[0]
+
+	if tname != oname
+		config_404 = configuration_data()
+		config_404.set('TARGET', '@0@.html'.format(tname))
+		c = configure_file(input : '404.rst',
+				   output : '@0@.rst'.format(oname),
+				   configuration : config_404,
+				   install : false)
+		dst_404s += [c]
+	endif
+endforeach
+
 src_extra = [
 	# dot drawings
 	'dot/seats-sketch.gv',
@@ -113,7 +179,7 @@ src_sphinx = custom_target('sphinx-sources',
 # do not use -j, it breaks on Ubuntu
 sphinx_output_dir = 'Documentation'
 custom_target('sphinx',
-	      input : [ sphinx_conf_py, git_version_page ] + src_rst + src_extra,
+	      input : [ sphinx_conf_py, git_version_page ] + src_rst + src_extra + dst_404s,
 	      output : [ sphinx_output_dir ],
 	      command : [ sphinx, '-q', '-b', 'html', '-a',
 			  meson.current_build_dir(), sphinx_output_dir],