title: How to change url_alias partially according to a pattern Drupal
body: <p>How to change url_alias partially according to a pattern?</p>
  
  <p>We have site with reports to users.
  We continue to update the reports with new content node but the url_alias kept same.
  For example, 
      /report/report_a
      /report/report_a/subreport_1
      /report/report_b
  …...
  Users bookmark the pages. So they can get into the reports directly.</p>
  
  <p>Recently we change the path pattern with /docs/ in front:
      /docs/report/report_a
      /docs/report/report_a/subreport_1
      /docs/report/report_b
  …...
  Now the new content nodes go to these url_alias.</p>
  
  <p>But the users have booked mark the pages.
  So we want to make them previous book marks, url_alias, can be redirected into the new path.
  For example, 
      /report/report_a to be redirected into /docs/report/report_a
      /report/report_a/subreport_1 to be redirected into<br>
      /docs/report/report_a/subreport_1</p>
  
  <p>That means to make /report/* paths to be redirectly to /docs/report/* paths
  Here * is wildcard.</p>