Add test checking the length of filepaths containing UTF-8 chars when
generating a diffstat with various `name-width`s.
Signed-off-by: LorenzoPegorari <lorenzo.pegorari2002@gmail.com>
[jc: fixed up t/meson.build to spell the name of the new test file correctly]
Signed-off-by: Junio C Hamano <gitster@pobox.com>