def additive_copytree(src, dst, symlinks=False, ignore=None):
if not os.path.exists(dst):<EOL><INDENT>os.makedirs(dst)<EOL><DEDENT>for item in os.listdir(src):<EOL><INDENT>s = os.path.join(src, item)<EOL>d = os.path.join(dst, item)<EOL>if os.path.isdir(s):<EOL><INDENT>additive_copytree(s, d, symlinks, ignore)<EOL><DEDENT>else:<EOL><INDENT>shutil.copy2(s, d)<EOL><DEDENT><DEDENT>
Version of `copytree` that merges into an existing directory.