Rework of show-server-revision

code/controllers/configuration.dm

@@ -56,6 +56,7 @@
 	var/wikiurl = "http://www.tgstation13.org/wiki" // Default wiki link.
 	var/forumurl = "http://tgstation13.org/phpBB/index.php" //default forums
 	var/rulesurl = "http://www.tgstation13.org/wiki/Rules" // default rules
+	var/githuburl = "https://www.github.com/tgstation/-tg-station" //default github
 
 	var/forbid_singulo_possession = 0
 	var/useircbot = 0
@@ -247,6 +248,8 @@
 					config.forumurl = value
 				if("rulesurl")
 					config.rulesurl = value
+				if("githuburl")
+					config.githuburl = value
 				if("guest_jobban")
 					config.guest_jobban = 1
 				if("guest_ban")