tuned;

--- a/src/Pure/Admin/build_doc.scala	Thu Mar 02 14:37:13 2017 +0100
+++ b/src/Pure/Admin/build_doc.scala	Thu Mar 02 15:46:27 2017 +0100
@@ -54,7 +54,7 @@
               progress, clean_build = true, max_jobs = max_jobs, system_mode = system_mode,
               sessions = sessions)
           if (res2.ok) {
-            val doc_dir = Path.explode("$ISABELLE_HOME/doc")
+            val doc_dir = Path.explode("~~/doc")
             for (doc <- selected_docs) {
               val name = Path.explode(doc + ".pdf")
               File.copy(output + name, doc_dir + name)