venv overwrites existing .gitignore

Bug report

Bug description

I cloned a github project with an existing .gitignore file.
I created a new python venv inside the cloned project using python3 -m venv .venv .
After creating the new venv, I see that the .gitignore file has been modified.

diff --git a/.gitignore b/.gitignore
index d0258704..f514b74c 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,17 +1,2 @@
-.dev
-.idea/
-.hypothesis/
-__pycache__/
-db.sqlite3
-*.sw*
-*.pyc
-venv/
-.venv/
-environment_settings.py
-elm-stuff/
-.coverage
-media
-docker/.env
-node_modules
-package-lock.json
-.sass-cache
+# Created by venv; see https://docs.python.org/3/library/venv.html
+*

I found this documentation on the mentioned url added to the .gitignore file:

Changed in version 3.13: venv now creates a .gitignore file for Git by default.

Environment

• Arch linux 6.14.9
• Python 3.13.3

Expected behaviour

I would expect it to not overwrite an existing .gitignore file, so it only creates it if it isnt present already.

Update

Using python3 -m venv .venv works as expected, but I did python3 -m venv .venv . (trailing dot) which creates a folder with a new venv named .venv, but also creates a venv inside the existing folder ., and that's when it overwrites the .gitignore

Please let me know if I'm missing some details or you need further testing for triage the issue.

CPython versions tested on:

3.13

Operating systems tested on:

Linux

Linked PRs

• gh-139130

在一個已經包含 .gitignore 的專案中使用 python3 -m venv .venv . 重現該行為，然後將其與 python3 -m venv .venv 進行比較。追蹤 python3 -m venv 的進入點，並驗證建立環境不會取代現有的 .gitignore；確認 Python 3.13 中的行為。