it does not assume you want to revert the parent of the first sha when reverting 2 shas

lib/gollum/frontend/app.rb

@@ -89,16 +89,11 @@ module Precious
       shas  = params[:splat].first.split("/")
       sha1  = shas.shift
       sha2  = shas.shift
-      sha1  = "#{sha1}^" if sha2
 
       if wiki.revert_page(@page, sha1, sha2, commit_message)
         redirect "/#{CGI.escape(@name)}"
       else
-        if sha2
-          sha1.chomp!('^')
-        else
-          sha2, sha1 = sha1, "#{sha1}^"
-        end
+        sha2, sha1 = sha1, "#{sha1}^" if !sha2
         @versions = [sha1, sha2]
         diffs     = wiki.repo.diff(@versions.first, @versions.last, @page.path)
         @diff     = diffs.first