specify github revision number in build parameters

libraries/build-docs.xml

@@ -1,5 +1,7 @@
 <project name="Kotlin standard library" default="document">
     <!-- Generates the standard library documentation using Dokka. -->
+    <property name="github.revision" value="master"/>
+
     <typedef resource="dokka-antlib.xml">
         <classpath>
             <fileset dir="${dokka.path}/lib">
@@ -17,7 +19,7 @@
         <dokka src="stdlib/src:../core/builtins:../core/reflection.jvm:../core/runtime.jvm/src/kotlin/jvm/annotations:../core/runtime.jvm/src/kotlin/jvm/JvmClassMapping.kt"
             samples="stdlib/test" outputDir="doc" moduleName="stdlib" skipDeprecated="true" outputFormat="kotlin-website"
             include="stdlib/src/Module.md">
-            <sourcelink path=".." url="http://github.com/JetBrains/kotlin/blob/master" linesuffix="#L"/>
+            <sourcelink path=".." url="http://github.com/JetBrains/kotlin/blob/${github.revision}" linesuffix="#L"/>
         </dokka>
     </target>