Word diff via colored diffs

[mgeisler]

I would love to have colors in the diff output. Colors can be super helpful since they can make it possible to implement word-diffs in the terminal.

An example could look like this (this is from Magit in a text-mode Emacs):

[mgeisler]

Let me mention that the excellent pretty-assertions crate also supports this kind of highlighting:

[hovinen]

In order to have a robust solution for this, we'll need to increase the minimum supported Rust version from 1.59 to 1.64. This is because we need a robust way to determine whether it is safe to produce ANSI sequences for stdout, and the one crate I can find for this, supports-color, has transitive dependencies which impose this requirement. The alternative would be to make the dependency optional, but this would lead to obscure behaviour which I really want to avoid.

This will also require fixing an issue I have discovered in supports-color itself.

Are you absolutely certain that bumping the minimum supported Rust version is okay? I consider that a one-way street, so we should only include this feature if there is really no doubt.

[mgeisler]

This is because we need a robust way to determine whether it is safe to produce ANSI sequences for stdout, and the one crate I can find for this, supports-color,

Can we not just use is_terminal as a start? That should do the usual thing which means colors when used in an interactive context and no colors otherwise.

[hovinen]

This is because we need a robust way to determine whether it is safe to produce ANSI sequences for stdout, and the one crate I can find for this, supports-color,

Can we not just use is_terminal as a start? That should do the usual thing which means colors when used in an interactive context and no colors otherwise.

That trait was made stable first in Rust 1.70.0, so we'd have to bump the MSRV even further.

We could directly use the crate which provides equivalent functionality, but its dependencies already require bumping the MSRV.

Either way, we'd then also lose the functionality provided by supports-color.

[mgeisler]

Can we not just use is_terminal as a start? That should do the usual thing which means colors when used in an interactive context and no colors otherwise.

That trait was made stable first in Rust 1.70.0, so we'd have to bump the MSRV even further.

Ah, silly me... I knew I should have looked more carefully 😄

We could directly use the crate which provides equivalent functionality, but its dependencies already require bumping the MSRV.

Either way, we'd then also lose the functionality provided by supports-color.

Right, but you know how long it takes to import a new crate into AOSP. Personally, I would use atty instead which answers the "are you a TTY?" question on both Unix and Windows (it is part of AOSP). It might not support the environment variables, but it should do the right thing in the vast majority of cases.