gitweb: Add a few comments about %feature hash

Signed-off-by: Jakub Narebski <jnareb@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

gitweb/gitweb.perl

@@ -98,10 +98,13 @@ our %feature = (
 	# 	'override' => allow-override (boolean),
 	# 	'default' => [ default options...] (array reference)}
 	#
-	# if feature is overridable (it means that allow-override has true value,
+	# if feature is overridable (it means that allow-override has true value),
 	# then feature-sub will be called with default options as parameters;
 	# return value of feature-sub indicates if to enable specified feature
 	#
+	# if there is no 'sub' key (no feature-sub), then feature cannot be
+	# overriden
+	#
 	# use gitweb_check_feature(<feature>) to check if <feature> is enabled
 
 	# Enable the 'blame' blob view, showing the last commit that modified
@@ -134,6 +137,7 @@ our %feature = (
 
 	# Enable text search, which will list the commits which match author,
 	# committer or commit text to a given string.  Enabled by default.
+	# Project specific override is not supported.
 	'search' => {
 		'override' => 0,
 		'default' => [1]},