Incorrect and inconsistent End-Of-Line characters in .gitmodules after "git submodule set-branch --branch <branch_name>"

Hello,

Originally this bug was reported in the Git for Windows project and
contains two screenshots:
https://github.com/git-for-windows/git/issues/3321
Johannes Schindelin (dscho) is convinced that this is not a
Windows-specific issue. Following is a brief description of this bug
as I've faced it:

After running the "git submodule set-branch --branch master -- ms1"
I've noticed that the .gitmodules file is encoded with both DOS and
UNIX End-of-Line characters simultaneously: all original lines use DOS
EOL characters but the added "branch = master" line uses UNIX EOL.

Found on the following environment:

$ git --version --build-options
git version 2.32.0.windows.2
cpu: x86_64
built from commit: 3d45ac813c4adf97fe3733c1f763ab6617d5add5
sizeof-long: 4
sizeof-size_t: 8
shell-path: /bin/sh
feature: fsmonitor--daemon

$ cmd.exe /c ver

Microsoft Windows [Version 10.0.19042.1083]

$ cat /etc/install-options.txt

Editor Option: VIM
Custom Editor Path:
Default Branch Option:
Path Option: Cmd
SSH Option: OpenSSH
Tortoise Option: false
CURL Option: OpenSSL
CRLF Option: CRLFAlways
Bash Terminal Option: MinTTY
Git Pull Behavior Option: Merge
Use Credential Manager: Core
Performance Tweaks FSCache: Enabled
Enable Symlinks: Enabled
Enable Pseudo Console Support: Disabled
Enable FSMonitor: Disabled

Comments of Johannes Schindelin (dscho) in the GitHub bug report:

I don't believe that Git considers its config files free game regarding line endings.
Therefore, I think that having DOS line endings in there is already a violation of Git's
assumptions. In any case, this is not a Windows-specific issue, even if DOS line
endings are much more prevalent on Windows than on other platforms. Please take
it to the Git mailing list (send plain-text messages, HTML messages are dropped
silently).