typing: add typehints to mercurial/diffutil.py
Lack of typehints here caused the fact that TortoiseHg was passing str instead
of bytes as the key in `opts` to be missed, resulting in shelf corruption in
cases where `diff.git` is required.
# See http://EditorConfig.org for the specification
root = true
[*.py]
indent_size = 4
indent_style = space
trim_trailing_whitespace = true
end_of_line = lf
[*.{c,h}]
indent_size = 8
indent_style = tab
trim_trailing_whitespace = true
end_of_line = lf
[*.t]
indent_size = 2
indent_style = space
trim_trailing_whitespace = false
end_of_line = lf