Don't prepend tagbase to tags if they start with "./" or "/".

That syntax made little sense previously, and this allows sites to put
"most" of their tags under $tagbase.

IkiWiki/Plugin/tag.pm

@@ -25,7 +25,8 @@ sub getopt () { #{{{
 sub tagpage ($) { #{{{
 	my $tag=shift;
 			
-	if (exists $config{tagbase} &&
+	if ($tag !~ m{^\.?/} &&
+	    exists $config{tagbase} &&
 	    defined $config{tagbase}) {
 		$tag=$config{tagbase}."/".$tag;
 	}

doc/plugins/tag.mdwn

@@ -24,6 +24,12 @@ tags/tech, tags/life, and tags/linux. This is a useful way to avoid
 having to write the full path to tags, if you want to keep them grouped
 together out of the way.
 
+If you want to override the tagbase for a particular tag, you can use
+something like this:
+
+	\[[!tag ./foo]]
+	\[[!taglink /foo]]
+
 [[!if test="enabled(tag)" then="""
 This wiki has the tag plugin enabled, so you'll see a note below that this
 page is tagged with the "tags" tag.