Merged bug fix from Stable into Unstable

build.xml

@@ -891,7 +891,7 @@
 
 
     <!-- Build a package consisting of all supporting files. Don't call this target directly. Call one of the specific packaging targets below -->
-    <target name="package" depends="dist,stage,require.executable" description="bundle up an executable for distribution">
+    <target name="package" depends="require.clean,dist,stage,require.executable" description="bundle up an executable for distribution">
       <mkdir dir="${package.output.dir}" />
       <xslt destdir="${package.output.dir}" style="${package.xml.dir}/CreatePackager.xsl" useImplicitFileset="false">
           <flattenmapper/>
@@ -1011,6 +1011,24 @@
         <delete dir="${pipelinetest.dir}"/>
     </target>
 
+    <!-- Depend on this target if your target requires a clean working directory but you don't want to depend on clean directly -->
+    <target name="require.clean">
+        <condition property="not.clean">
+            <or>
+                <available file="${build.dir}" />
+                <available file="${lib.dir}" />
+                <available file="${contract.dump.dir}" />
+                <available file="${staging.dir}" />
+                <available file="${dist.dir}" />
+                <available file="${pipelinetest.dir}" />
+                <available file="${javadoc.dir}" />
+                <available file="${scaladoc.dir}" />
+                <available file="${gatkdocs.dir}" />
+            </or>
+        </condition>
+        <fail message="Selected build target requires a clean working directory. Run ant clean and then try again." if="not.clean" />
+    </target>
+
 
     <!-- ******************************************************************************** -->
     <!-- gsalib                                                                           -->