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
+        sha2, sha1 = sha1, "#{sha1}^" if !sha2
-          sha1.chomp!('^')
-        else
-          sha2, sha1 = sha1, "#{sha1}^"
-        end
         @versions = [sha1, sha2]
         diffs     = wiki.repo.diff(@versions.first, @versions.last, @page.path)
         @diff     = diffs.first

test/test_app.rb

@@ -113,7 +113,7 @@ context "Frontend" do
   test "reverts multiple commits" do
     page1 = @wiki.page('A')
 
-    post "/revert/A/302a5491a9a5ba12c7652ac831a44961afa312d2/b26b791cb7917c4f37dd9cb4d1e0efb24ac4d26f"
+    post "/revert/A/fc66539528eb96f21b2bbdbf557788fe8a1196ac/b26b791cb7917c4f37dd9cb4d1e0efb24ac4d26f"
     follow_redirect!
     assert last_response.ok?