rustdoc: The short description of #[doc(cfg(target_feature = ...))] shouldn't spell out "target feature"

[kennytm]

• Repro: https://doc.rust-lang.org/nightly/core/arch/x86_64/index.html
• Discussion: https://twitter.com/QuietMisdreavus/status/977567670131359744

rustdoc's short description of #[doc(cfg(target_feature = ...))] is showing something like [x86-64 and target feature avx]. The words "target feature" is unnecessary since usually it is clear what avx means from context, i.e. [x86-64 and avx] should be clear enough.

[QuietMisdreavus]

Notes to self:

The issue at hand is the fact that the "short text" is overridden when the condition is combined with others. The target features are supposed to only show "avx" when they're by themselves, as shown in the OP of #48759. The offending snippet:

rust/src/librustdoc/clean/cfg.rs

Lines 410 to 419 in 31ae4f9

	impl<'a> fmt::Display for ShortHtml<'a> {
	fn fmt(&self, fmt: &mut fmt::Formatter) -> fmt::Result {
	match *self.0 {
	Cfg::Cfg(ref name, Some(ref vendor)) if name == &"target_feature" => {
	write!(fmt, "<code>{}</code>", vendor)
	},
	ref cfg => write!(fmt, "{}", Html(cfg)),
	}
	}
	}

The easiest way to fix this is to never print "target feature", even in the long form, but that text is still valuable there.