Delete git-auto-svn and its docs

git_cl.py

 #!/usr/bin/env python
 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Copyright (C) 2008 Evan Martin <martine@danga.com>
 
 """A git-command for integrating reviews on Rietveld and Gerrit."""
 
 from __future__ import print_function
@@ skipping 4382 matching lines @@
   """True if retrying push won't help."""
   return '(prohibited by Gerrit)' in push_stdout
 
 
 @subcommand.usage('[upstream branch to apply against]')
 def CMDdcommit(parser, args):
   """Commits the current changelist via git-svn."""
   if not settings.GetIsGitSvn():
     if git_footers.get_footer_svn_id():
       # If it looks like previous commits were mirrored with git-svn.
-      message = """This repository appears to be a git-svn mirror, but no
-upstream SVN master is set. You probably need to run 'git auto-svn' once."""
+      message = """This repository appears to be a git-svn mirror, but we
+don't support git-svn mirrors anymore."""
     else:
       message = """This doesn't appear to be an SVN repository.
 If your project has a true, writeable git repository, you probably want to run
 'git cl land' instead.
 If your project has a git mirror of an upstream SVN master, you probably need
 to run 'git svn init'.
 
 Using the wrong command might cause your commit to appear to succeed, and the
 review to be closed, without actually landing upstream. If you choose to
 proceed, please verify that the commit lands upstream as expected."""
@@ skipping 881 matching lines @@
 if __name__ == '__main__':
   # These affect sys.stdout so do it outside of main() to simplify mocks in
   # unit testing.
   fix_encoding.fix_encoding()
   setup_color.init()
   try:
     sys.exit(main(sys.argv[1:]))
   except KeyboardInterrupt:
     sys.stderr.write('interrupted\n')
     sys.exit(1)