Issue 4319 - [hgreview] Make sure reviews for the initial repository revision can be created

hgreview.py

Index: hgreview.py
===================================================================
--- a/hgreview.py
+++ b/hgreview.py
@@ -42,17 +42,18 @@ def review(ui, repo, *paths, **opts):
         args.append('--quiet')
 
     if not opts.get('issue') or opts.get('message'):
         args.append('--send_mail')
 
     if opts.get('revision') and opts.get('change'):
         raise error.Abort('Ambiguous revision range, only one of --revision and --change can be specified.')
     if opts.get('change'):
-        args.extend(['--rev', '{0}^:{0}'.format(opts['change'])])
+        rev = repo[opts['change']]
+        args.extend(['--rev', '{}:{}'.format(rev.parents()[0], rev)])
     elif opts.get('revision'):
         args.extend(['--rev', opts['revision']])
     else:
         raise error.Abort('What should be reviewed? Either --revision or --change is required.')
 
     if not opts.get('issue'):
         # New issue, make sure title and message are set
         if not opts.get('title') and opts.get('change'):