g.extension: example to download specific version from GRASS Addons (closes https://trac.osgeo.org/grass/ticket/2896)

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@72792 15284696-431f-4ddb-bdfa-cd5b030d7da7

scripts/g.extension/g.extension.html

@@ -202,6 +202,17 @@ g.extension r.example url=http://example.com/.../r.example?format=zip
 Note that because of MS-Windows operating system architecture,
 only official repository is supported on this platform.
 
+<h3>Install a specific version from Addons</h3>
+
+To install a specific version from GRASS GIS Addons, specify the full
+URL pointing to Trac code browser and include Subversion revision
+number. For example, this installs the version number 57854 of
+r.local.relief module:
+
+<div class="code"><pre>
+g.extension r.local.relief url="https://trac.osgeo.org/grass/browser/grass-addons/grass7/raster/r.local.relief?rev=57854&amp;format=zip"
+</pre></div>
+
 <h3>Installing when writing a module locally</h3>
 
 Having source code of a GRASS module in a directory on disk