title repeated twice when title_format is set

[BayerSe]

First of all, I would like to thank everyone working on this project. It eases our changelog generation a lot!

After upgrading our dependencies I have spotted some changed behavior. To illustrate this, I have created a fresh Python 3.9.4 project with just minimal code and towncrier==21.3.0.

When I configure towncrier like this:

[tool.towncrier]
title_format = "{version} ({project_date})"

Then the output of towncrier build --version=0.1 --draft is

0.1 (2021-04-27)
=================

Features
--------

- This is only a test. (#1)

as expected. However, the content of NEWS.rst after towncrier build --version=0.1 is

0.1 (2021-04-27)0.1 (2021-04-27)
================

Features
--------

- This is only a test. (#1)

where we can see that the title is duplicated.

[hynek]

I suspect this is related to #340 too

[saimn]

We have the same issue (astropy/astropy#12083). The problem seems to be that top_line is both written by the code (

towncrier/src/towncrier/_writer.py

Lines 41 to 42 in 5dce0fa

	f.write(top_line.encode("utf8"))
	f.write(content.encode("utf8"))

) and present in the default template. I guess it just be written only with the template.

[kasium]

@adiroiban can you please release a new version with the fix

[adiroiban]

PR here . #360
Please check that the release candidate is ok https://pypi.org/project/towncrier/21.9.0rc1/

thanks!

[decaz]

@adiroiban is stable version can be released now, please?

CC @graingert @altendky @hukkin