Since https://github.com/rust-lang/rust/pull/95503, `library/std` means
"build just std and its dependencies"; to get the old behavior that built
`proc_macro` and `test`, you need `x build library`.
- Update `library/std` to `library`
- Remove the `-i` suggestions; `incremental = true` is already the default for most profiles, in
which case `-i` does nothing. If you don't have incremental enabled, I still think suggesting `-i`
is bad idea, because it's easy to forget once, at which point you'll end up rebuilding the whole
compiler / standard library.
- Remove a few repetitive sections and don't discuss incremental in such detail
Incremental works well enough that it should "just work" for most people;
I don't think it needs multiple paragraphs of explanation so early in the guide.
- Clarify that `test library/std` *only* tests libstd in a few places
This is a follow-up to #1279.
The "Getting Started" chapter is, TBH, pretty bad when it comes to the
stuff about building and testing. It has far too much detail and lots of
repetition, which would be overwhelming to a newcomer.
This commit removes most of it, leaving behind just quick mentions of
the most common `x.py` commands: `check`, `build`, `test`, `fmt`, with
links to the appropriate chapters for details. There were a few
interesting details that weren't covered elsewhere, so I moved those
into other chapters.
* Rename "The walking tour of rustdoc" to "Rustdoc overview",
which I think is a more accurate name
* Use same name in sidebar TOC as in chapter text
* Make links between the two chapters prominent
* Convert a few `.html` links to `.md`
Probably we should just merge the chapters, but leaving that for later.