metadata.xsd: Add straight-to-stable element

Bug: https://bugs.gentoo.org/974436
Signed-off-by: Ulrich Müller <ulm@gentoo.org>

metadata.xsd

@@ -24,6 +24,10 @@
 			<xs:selector xpath='stabilize-allarches'/>
 			<xs:field xpath='@restrict'/>
 		</xs:unique>
+		<xs:unique name='straightToStableUniquityConstraint'>
+			<xs:selector xpath='straight-to-stable'/>
+			<xs:field xpath='@restrict'/>
+		</xs:unique>
 		<xs:unique name='upstreamSingleConstraint'>
 			<xs:selector xpath='upstream'/>
 			<xs:field xpath='@fake-only-once'/>
@@ -65,6 +69,7 @@
 				</xs:unique>
 			</xs:element>
 			<xs:element name='stabilize-allarches' type='stabilizeAllArchesType'/>
+			<xs:element name='straight-to-stable' type='straightToStableType'/>
 			<xs:element name='upstream' type='upstreamType'>
 				<xs:unique name='upstreamMaintainerUniquityConstraint'>
 					<xs:selector xpath='maintainer'/>
@@ -224,6 +229,11 @@
 			default=''/>
 	</xs:complexType>
 
+	<!-- straight-to-stable -->
+	<xs:complexType name='straightToStableType'>
+		<xs:attribute name='restrict' type='restrictAttrType' default=''/>
+	</xs:complexType>
+
 	<!-- use flags -->
 	<xs:complexType name='useType'>
 		<xs:choice minOccurs='0' maxOccurs='unbounded'>