Forgot to commit those files before...

app/views/issues/_changeset_github.rhtml

@@ -0,0 +1,7 @@
+<div class="changeset <%= cycle('odd', 'even') %>">
+<p><% link_to(url_for_revision) do %><%="#{l(:label_revision)} #{changeset.format_identifier}" %><% end %><br />
+    <span class="author"><%= authoring(changeset.committed_on, changeset.author) %></span></p>
+<div class="changeset-changes">
+    <%= textilizable(changeset, :comments) %>
+</div>
+</div>

lib/issue_changeset_listener.rb

@@ -0,0 +1,22 @@
+class IssueChangesetListener < Redmine::Hook::ViewListener
+
+  def view_issue_show_changeset(context)
+    changeset = context[:changeset]
+
+    projects_github = Setting.plugin_redmine_issue_changesets_view_link_github
+    github_repo = nil
+    github_repo = projects_github[changeset.project.identifier] unless projects_github.blank?
+
+    unless github_repo.blank?
+      url = "https://github.com/%s/commit/%s" % [github_repo, changeset.identifier]
+    else
+      rev = changeset.respond_to?(:identifier) ? revision.identifier : revision
+      url = url_for({:controller => 'repositories', :action => 'revision', :id => project.identifier, :rev => rev})
+    end
+    context[:controller].send(:render_to_string, {
+                                :partial => "changeset_github",
+                                :locals  => context.merge({:url_for_revision=>url})
+                              })
+  end
+
+end