Delete git-auto-svn and its docs

git_cl.py

Index: git_cl.py
diff --git a/git_cl.py b/git_cl.py
index 1b016d46137da6b67efc7bdfdf52dac0ea0e9c8c..dbf0d2c64d5a27e1d20f8e7e43d5f0d75077e1b7 100755
--- a/git_cl.py
+++ b/git_cl.py
@@ -4400,8 +4400,8 @@ def CMDdcommit(parser, args):
   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