diff -r 292b97e17fb7 -r f3bbb9ca57d6 doc-src/System/Thy/Sessions.thy
--- a/doc-src/System/Thy/Sessions.thy	Wed Aug 08 14:45:40 2012 +0200
+++ b/doc-src/System/Thy/Sessions.thy	Wed Aug 08 15:58:40 2012 +0200
@@ -192,10 +192,11 @@
 Usage: isabelle build [OPTIONS] [SESSIONS ...]
 
   Options are:
+    -D DIR       include session directory and select its sessions
     -a           select all sessions
     -b           build heap images
     -c           clean build
-    -d DIR       include session directory with ROOT file
+    -d DIR       include session directory
     -g NAME      select session group NAME
     -j INT       maximum number of parallel jobs (default 1)
     -n           no build -- test dependencies only
@@ -235,6 +236,9 @@
   The build tool takes session dependencies into account: the set of
   selected sessions is completed by including all ancestors.
 
+  \medskip Option @{verbatim "-D"} is similar to @{verbatim "-d"}, but
+  selects all sessions that are defined in the given directories.
+
   \medskip The build process depends on additional options
   (\secref{sec:system-options}) that are passed to the prover
   eventually.  The settings variable @{setting_ref
@@ -315,6 +319,13 @@
 \begin{ttbox}
 isabelle build -a -n -c
 \end{ttbox}
+
+  \smallskip Build all sessions from some other directory hierarchy,
+  according to the settings variable @{verbatim "AFP"} that happens to
+  be defined inside the Isabelle environment:
+\begin{ttbox}
+isabelle build -D '$AFP'
+\end{ttbox}
 *}