Thank you for filling out a Git bug report!
Please answer the following questions to help us understand your issue.

What did you do before the bug happened? (Steps to reproduce your issue)

I did:
$git init
$git add Program.cs
Inside:
{
 Console.Writeline("1");
 Console.Readline();
}
$git commit -m "Init commit"

$git checkout -b dev
Did this changes in Program.cs:
{
 Console.Writeline("1");
 Console.Readline();
 Console.Readline();
 Console.Readline();
}
$git commit -a -m "dev commit"

$git checkout master
Did this changes in Program.cs:
{
 Console.Writeline("1");
 Console.Writeline("2");
 Console.Readline();
 Console.Readline();
}
$git commit -a -m "master commit"

And I get a logical bug inside Program.cs when I want merge or rebase:
1)git merge dev
OR
2)git rebase dev
 
What did you expect to happen? (Expected behavior)
I expected conflict in my Program.cs like:
{
 Console.Writeline("1");
<<<<<<< HEAD
 Console.Writeline("2");
=======
 Console.Readline();
>>>>>>> dev
 Console.Readline();
 Console.Readline();
}

What happened instead? (Actual behavior)
Just sum of 2 commits without any conflicts:
{
 Console.Writeline("1");
 Console.Writeline("2");
 Console.Readline();
 Console.Readline();
 Console.Readline();
 Console.Readline();
}

What's different between what you expected and what actually happened?
Extra lines was added in "silent" mode without any notification.

Anything else you want to add:
Now necessary to revice all lines, even if there are no any conflicts :(

[System Info]
git version:
git version 2.32.0.windows.1
cpu: x86_64
built from commit: 4c204998d0e156d13d81abe1d1963051b1418fc0
sizeof-long: 4
sizeof-size_t: 8
shell-path: /bin/sh
feature: fsmonitor--daemon
uname: Windows 6.1 7601 
compiler info: gnuc: 10.3
libc info: no libc information available
$SHELL (typically, interactive shell): <unset>


[Enabled Hooks]