g.version manual: more on "revision=exported"

general/g.version/g.version.html

@@ -70,7 +70,9 @@ sqlite=3.26.0
 </pre></div>
 
 Note: if <tt>revision=exported</tt> is reported instead of the git hash then the
-<tt>git</tt> program was not available during compilation of GRASS GIS.
+<tt>git</tt> program was not available during compilation of GRASS GIS and the
+source code did not contain the <tt>.git/</tt> subdirectory (requires e.g. to
+<tt>git clone</tt> the GRASS GIS <a href="https://github.com/OSGeo/grass/">software repository</a>.)
 
 <h2>Citing GRASS GIS</h2>