Mercurial used to enable colors via an extension. Nowadays that is not true
anymore and `extensions.color=!` is rendered useless. Use the omnipresent
`--color=never` instead.
`defaults` is deprecated in favor of `aliases`. We use `aliases.diff=` to force
the use of the standard diff behaviour of `hg diff` which is the same as from
GNU diff. Otherwise an external diff tool could produce output that signify does
not understand.
Refrences #272
4e7faba8d3