D5485: log: fixes line wrap on diffstat (issue5800)

[Yuya Nishihara]

> -        return max(i * graphwidth // maxtotal, int(bool(i)))
> +        return max(i * graphwidth // max(diffstatsum(stats)), int(bool(i)))

Doesn't look correct. Why taking max of
`(maxname, maxtotal, totaladds, totalremoves, hasbinary)`?

IIUC, the problem is that the `width` parameter is incorrect because of
graph lines.