bookmarks: set the current bookmark to the new name if we rename the current bookmark

If we rename the current bookmark, we have to set the current bookmark
to the new name.

hgext/bookmarks.py

@@ -64,9 +64,9 b' def write(repo, refs):'
     '''
     if os.path.exists(repo.join('bookmarks')):
         util.copyfile(repo.join('bookmarks'), repo.join('undo.bookmarks'))
-    file = repo.opener('bookmarks', 'w+')
     if current(repo) not in refs:
         setcurrent(repo, None)
+    file = repo.opener('bookmarks', 'w+')
     for refspec, node in refs.items():
         file.write("%s %s\n" % (hex(node), refspec))
     file.close()
@@ -138,6 +138,8 b' def bookmark(ui, repo, mark=None, rev=No'
             raise util.Abort(_("new bookmark name required"))
         marks[mark] = marks[rename]
         del marks[rename]
+        if current(repo) == rename:
+            setcurrent(repo, mark)
         write(repo, marks)
         return