Added tags

Command-line.md

@@ -8,6 +8,7 @@ Note that options are described according to the following pattern:
 <a href="#usage">    `    -h, -?, --help`</a><br />
 <a href="#nothrow">  `    -n, --nothrow`</a><br />
 <a href="#test">     `    -t, --test`</a><br />
+<a href="#tags">     `    -g, --tag`</a><br />
 <a href="#reporter"> `    -r, --reporter`</a><br />
 <a href="#break">    `    -b, --break`</a><br />
 <a href="#success">  `    -s, --success`</a><br />
@@ -59,6 +60,26 @@ Examples:
                                start with 'a/b/', except 'a/b/c', which is included
 </pre>
 
+<br />
+
+<a name="tags" />
+<pre>
+-g, --tag  &lt;tagspec> [, &lt;tagspec> ...]
+</pre>
+
+This option allows one or more tags or tag patterns to be specified.
+Each tag is enclosed in square brackets. A series of tags form an AND expression wheras a comma seperated sequence forms an OR expression. e.g.:
+  
+      -g [one][two],[three]
+  
+This matches all tests tagged [one] and [two], as well as all tests tagged [three].
+
+Tags can be negated with the ~ character. This removed matching tests from the set. e.g.:
+  
+    -g [one]~[two]
+  
+matches all tests tagged [one], except those also tagged [two]
+
 <a name="reporter" />
 ## Choosing a reporter to use