Bug? I can't manually merge changes with difftool

When I run

git difftool main HEAD

and manually merge changes in started meld or kdiff3 and then save the
resulting file, it is saved somewhere in /tmp not in the workdir.
Workdir is not modified after I close meld or kdiff3.

I need to store changes in workdir.

Is it a bug of Git 2.27.0.