gsettings: Install gettext ITS rules

Recent gettext has a feature to allow consumer projects to supply their
own string extraction rules for XML files, in ITS format.

Gettext still ships the rule for *.gschema.xml, but it would be better
maintained in the upstream project.

See the gettext documentation for details:
http://www.gnu.org/software/gettext/manual/html_node/Preparing-ITS-Rules.html

https://bugzilla.gnome.org/show_bug.cgi?id=760199

gio/Makefile.am

@@ -746,6 +746,9 @@ gsettings_SOURCES = gsettings-tool.c
 schemadir = $(datadir)/glib-2.0/schemas
 dist_schema_DATA = gschema.dtd
 
+itsdir = $(datadir)/gettext/its
+dist_its_DATA = gschema.loc gschema.its
+
 # ------------------------------------------------------------------------
 # gdbus(1) tool
 

gio/gschema.its

@@ -0,0 +1,25 @@
+<?xml version="1.0"?>
+<!--
+See the gettext documentation for the file format:
+http://www.gnu.org/software/gettext/manual/html_node/Preparing-ITS-Rules.html
+-->
+<its:rules xmlns:its="http://www.w3.org/2005/11/its"
+           xmlns:gt="https://www.gnu.org/s/gettext/ns/its/extensions/1.0"
+           version="2.0">
+  <its:translateRule selector="/schemalist" translate="no"/>
+
+  <its:translateRule selector="//summary | //description" translate="yes"/>
+
+  <its:translateRule selector="//default[@l10n]" translate="yes"/>
+
+  <!-- The 'context' attribute should be extracted as msgctxt.  -->
+  <gt:contextRule selector="//default[@context]" contextPointer="@context"/>
+  <gt:escapeRule selector="//default/@context" escape="no"/>
+
+  <!-- Remove whitespaces around the default value.  -->
+  <gt:preserveSpaceRule selector="//default" space="trim"/>
+
+  <!-- Extracted strings are consumed by the library and are never
+       merged back; we don't want to escape special characters.  -->
+  <gt:escapeRule selector="/schemalist" escape="no"/>
+</its:rules>

gio/gschema.loc

@@ -0,0 +1,10 @@
+<?xml version="1.0"?>
+<!--
+See the gettext documentation for the file format:
+http://www.gnu.org/software/gettext/manual/html_node/Preparing-ITS-Rules.html
+-->
+<locatingRules>
+  <locatingRule name="GSettings" pattern="*.gschema.xml">
+    <documentRule localName="schemalist" target="gschema.its"/>
+  </locatingRule>
+</locatingRules>