scm: git: get "extra_report_last_commit" value from extra_info (#8365, #7047).

Browsing repository tree performance problem is git only.
So, adding new "report_last_commit" column is very expensive.

git-svn-id: svn+ssh://rubyforge.org/var/svn/redmine/trunk@5768 e93f8b46-1217-0410-a6f0-8f06a7374b81

app/models/repository/git.rb

@@ -39,7 +39,10 @@ class Repository::Git < Repository
   end
 
   def extra_report_last_commit
-    true
+    return false if extra_info.nil?
+    v = extra_info["extra_report_last_commit"]
+    return false if v.nil?
+    v.to_s != '0'
   end
 
   def supports_directory_revisions?