rustdoc: link to stable/beta docs consistently in documentation

 ## User-facing changes

- Intra-doc links to primitives that currently go to rust-lang.org/nightly/std/primitive.x.html will start going to channel that rustdoc was built with. Nightly will continue going to /nightly; Beta will link to /beta; stable compilers will link to /1.52.1 (or whatever version they were built as).
- Cross-crate links from std to core currently go to /nightly unconditionally. They will start going to /1.52.0 on stable channels (but remain the same on nightly channels).
- Intra-crate links from std to std (or core to core) currently go to the same URL they are hosted at; they will continue to do so. Notably, this is different from everything else because it can preserve the distinction between /stable and /1.52.0 by using relative links.

Note that "links" includes both intra-doc links and rustdoc's own
automatically generated hyperlinks.

 ## Implementation changes

- Update the testsuite to allow linking to /beta and /1.52.1 in docs
- Use an html_root_url for the standard library that's dependent on the channel

  This avoids linking to nightly docs on stable.

- Update rustdoc to use channel-dependent links for primitives from an
  unknown crate

- Set DOC_RUST_LANG_ORG_CHANNEL from bootstrap to ensure it's in sync
- Include doc.rust-lang.org in the channel

1 files changed, 10 insertions, 10 deletions

diff --git a/src/test/rustdoc/intra-doc/primitive-non-default-impl.rs b/src/test/rustdoc/intra-doc/primitive-non-default-impl.rs
index cf83ead4db7..f8a824bd08f 100644
--- a/src/test/rustdoc/intra-doc/primitive-non-default-impl.rs
+++ b/src/test/rustdoc/intra-doc/primitive-non-default-impl.rs
@@ -3,29 +3,29 @@
 
 // @has primitive_non_default_impl/fn.str_methods.html
 /// [`str::trim`]
-// @has - '//*[@href="https://doc.rust-lang.org/nightly/std/primitive.str.html#method.trim"]' 'str::trim'
+// @has - '//*[@href="{{channel}}/std/primitive.str.html#method.trim"]' 'str::trim'
 /// [`str::to_lowercase`]
-// @has - '//*[@href="https://doc.rust-lang.org/nightly/std/primitive.str.html#method.to_lowercase"]' 'str::to_lowercase'
+// @has - '//*[@href="{{channel}}/std/primitive.str.html#method.to_lowercase"]' 'str::to_lowercase'
 /// [`str::into_boxed_bytes`]
-// @has - '//*[@href="https://doc.rust-lang.org/nightly/std/primitive.str.html#method.into_boxed_bytes"]' 'str::into_boxed_bytes'
+// @has - '//*[@href="{{channel}}/std/primitive.str.html#method.into_boxed_bytes"]' 'str::into_boxed_bytes'
 /// [`str::replace`]
-// @has - '//*[@href="https://doc.rust-lang.org/nightly/std/primitive.str.html#method.replace"]' 'str::replace'
+// @has - '//*[@href="{{channel}}/std/primitive.str.html#method.replace"]' 'str::replace'
 pub fn str_methods() {}
 
 // @has primitive_non_default_impl/fn.f32_methods.html
 /// [f32::powi]
-// @has - '//*[@href="https://doc.rust-lang.org/nightly/std/primitive.f32.html#method.powi"]' 'f32::powi'
+// @has - '//*[@href="{{channel}}/std/primitive.f32.html#method.powi"]' 'f32::powi'
 /// [f32::sqrt]
-// @has - '//*[@href="https://doc.rust-lang.org/nightly/std/primitive.f32.html#method.sqrt"]' 'f32::sqrt'
+// @has - '//*[@href="{{channel}}/std/primitive.f32.html#method.sqrt"]' 'f32::sqrt'
 /// [f32::mul_add]
-// @has - '//*[@href="https://doc.rust-lang.org/nightly/std/primitive.f32.html#method.mul_add"]' 'f32::mul_add'
+// @has - '//*[@href="{{channel}}/std/primitive.f32.html#method.mul_add"]' 'f32::mul_add'
 pub fn f32_methods() {}
 
 // @has primitive_non_default_impl/fn.f64_methods.html
 /// [`f64::powi`]
-// @has - '//*[@href="https://doc.rust-lang.org/nightly/std/primitive.f64.html#method.powi"]' 'f64::powi'
+// @has - '//*[@href="{{channel}}/std/primitive.f64.html#method.powi"]' 'f64::powi'
 /// [`f64::sqrt`]
-// @has - '//*[@href="https://doc.rust-lang.org/nightly/std/primitive.f64.html#method.sqrt"]' 'f64::sqrt'
+// @has - '//*[@href="{{channel}}/std/primitive.f64.html#method.sqrt"]' 'f64::sqrt'
 /// [`f64::mul_add`]
-// @has - '//*[@href="https://doc.rust-lang.org/nightly/std/primitive.f64.html#method.mul_add"]' 'f64::mul_add'
+// @has - '//*[@href="{{channel}}/std/primitive.f64.html#method.mul_add"]' 'f64::mul_add'
 pub fn f64_methods() {}