Should CI environments infer `ColorChoice::Always`?

[woodruffw]

Context: I was trying to figure out why CI environments (i.e. CI=true and similar) weren't being colorized by default when using anstream to plumb output containing ANSI colors. I ended up on this choice implementation:

anstyle/crates/anstream/src/auto.rs

Lines 197 to 223 in cbad464

	#[cfg(feature = "auto")]
	fn choice(raw: &dyn RawStream) -> ColorChoice {
	let choice = ColorChoice::global();
	match choice {
	ColorChoice::Auto => {
	let clicolor = anstyle_query::clicolor();
	let clicolor_enabled = clicolor.unwrap_or(false);
	let clicolor_disabled = !clicolor.unwrap_or(true);
	if anstyle_query::no_color() {
	ColorChoice::Never
	} else if anstyle_query::clicolor_force() {
	ColorChoice::Always
	} else if clicolor_disabled {
	ColorChoice::Never
	} else if raw.is_terminal()
	&& (anstyle_query::term_supports_color()
	|| clicolor_enabled
	|| anstyle_query::is_ci())
	{
	ColorChoice::Always
	} else {
	ColorChoice::Never
	}
	}
	ColorChoice::AlwaysAnsi | ColorChoice::Always | ColorChoice::Never => choice,
	}
	}

If my read of that helper is right, the current logic only considers anstyle_query::is_ci() after raw.is_terminal() is satisfied. In practice that means that ColorChoice::Always branch won't be taken for CI environments, since (AFAIK) most CI environments don't actually provide a terminal (they support ANSI color codes, but they won't provide a true pty that would pass is is_terminal() check).

Given that, does it makes sense to split that check out, so that is_ci() becomes a sufficient condition for ColorChoice::Always? My intuition is "yes" (since the CI check seems to be a no-op as is), but there's also some nuance given that CI environments aren't real terminals and might only support a small subset of the escapes normally accepted by terminals (things like OSC codes in particular).

So, I don't have a super clear sense here, but I figured I'd open this in case others have a clearer picture than I do 😅. If this change makes sense, I'd be happy to send a PR for it.