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

8 files changed, 30 insertions, 26 deletions

diff --git a/src/test/rustdoc-ui/check.rs b/src/test/rustdoc-ui/check.rs
index 65a56e03d9d..2b44ba24b44 100644
--- a/src/test/rustdoc-ui/check.rs
+++ b/src/test/rustdoc-ui/check.rs
@@ -1,5 +1,6 @@
 // check-pass
 // compile-flags: -Z unstable-options --check
+// normalize-stderr-test: "nightly|beta|1\.[0-9][0-9]\.[0-9]" -> "$$CHANNEL"
 
 #![warn(missing_docs)]
 //~^ WARN
diff --git a/src/test/rustdoc-ui/check.stderr b/src/test/rustdoc-ui/check.stderr
index 2e1fc1eca4d..8c9e70e57fe 100644
--- a/src/test/rustdoc-ui/check.stderr
+++ b/src/test/rustdoc-ui/check.stderr
@@ -1,5 +1,5 @@
 warning: missing documentation for the crate
-  --> $DIR/check.rs:4:1
+  --> $DIR/check.rs:5:1
    |
 LL | / #![warn(missing_docs)]
 LL | |
@@ -10,13 +10,13 @@ LL | | pub fn foo() {}
    | |_______________^
    |
 note: the lint level is defined here
-  --> $DIR/check.rs:4:9
+  --> $DIR/check.rs:5:9
    |
 LL | #![warn(missing_docs)]
    |         ^^^^^^^^^^^^
 
 warning: missing documentation for a function
-  --> $DIR/check.rs:9:1
+  --> $DIR/check.rs:10:1
    |
 LL | pub fn foo() {}
    | ^^^^^^^^^^^^
@@ -24,16 +24,16 @@ LL | pub fn foo() {}
 warning: no documentation found for this crate's top-level module
    |
 note: the lint level is defined here
-  --> $DIR/check.rs:7:9
+  --> $DIR/check.rs:8:9
    |
 LL | #![warn(rustdoc::all)]
    |         ^^^^^^^^^^^^
    = note: `#[warn(rustdoc::missing_crate_level_docs)]` implied by `#[warn(rustdoc::all)]`
    = help: The following guide may be of use:
-           https://doc.rust-lang.org/nightly/rustdoc/how-to-write-documentation.html
+           https://doc.rust-lang.org/$CHANNEL/rustdoc/how-to-write-documentation.html
 
 warning: missing code example in this documentation
-  --> $DIR/check.rs:4:1
+  --> $DIR/check.rs:5:1
    |
 LL | / #![warn(missing_docs)]
 LL | |
@@ -44,14 +44,14 @@ LL | | pub fn foo() {}
    | |_______________^
    |
 note: the lint level is defined here
-  --> $DIR/check.rs:7:9
+  --> $DIR/check.rs:8:9
    |
 LL | #![warn(rustdoc::all)]
    |         ^^^^^^^^^^^^
    = note: `#[warn(rustdoc::missing_doc_code_examples)]` implied by `#[warn(rustdoc::all)]`
 
 warning: missing code example in this documentation
-  --> $DIR/check.rs:9:1
+  --> $DIR/check.rs:10:1
    |
 LL | pub fn foo() {}
    | ^^^^^^^^^^^^^^^
diff --git a/src/test/rustdoc-ui/intra-doc/email-address-localhost.rs b/src/test/rustdoc-ui/intra-doc/email-address-localhost.rs
index 417618c7458..9465e8e7ab9 100644
--- a/src/test/rustdoc-ui/intra-doc/email-address-localhost.rs
+++ b/src/test/rustdoc-ui/intra-doc/email-address-localhost.rs
@@ -1,3 +1,4 @@
+// normalize-stderr-test: "nightly|beta|1\.[0-9][0-9]\.[0-9]" -> "$$CHANNEL"
 #![deny(warnings)]
 
 //! Email me at <hello@localhost>.
diff --git a/src/test/rustdoc-ui/intra-doc/email-address-localhost.stderr b/src/test/rustdoc-ui/intra-doc/email-address-localhost.stderr
index f287f87408c..1b07828fc6e 100644
--- a/src/test/rustdoc-ui/intra-doc/email-address-localhost.stderr
+++ b/src/test/rustdoc-ui/intra-doc/email-address-localhost.stderr
@@ -1,16 +1,16 @@
 error: unknown disambiguator `hello`
-  --> $DIR/email-address-localhost.rs:3:18
+  --> $DIR/email-address-localhost.rs:4:18
    |
 LL | //! Email me at <hello@localhost>.
    |                  ^^^^^
    |
 note: the lint level is defined here
-  --> $DIR/email-address-localhost.rs:1:9
+  --> $DIR/email-address-localhost.rs:2:9
    |
 LL | #![deny(warnings)]
    |         ^^^^^^^^
    = note: `#[deny(rustdoc::broken_intra_doc_links)]` implied by `#[deny(warnings)]`
-   = note: see https://doc.rust-lang.org/nightly/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
+   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
 
 error: aborting due to previous error
 
diff --git a/src/test/rustdoc-ui/intra-doc/unknown-disambiguator.rs b/src/test/rustdoc-ui/intra-doc/unknown-disambiguator.rs
index 925fc515a3e..0aa1e5a415a 100644
--- a/src/test/rustdoc-ui/intra-doc/unknown-disambiguator.rs
+++ b/src/test/rustdoc-ui/intra-doc/unknown-disambiguator.rs
@@ -1,3 +1,4 @@
+// normalize-stderr-test: "nightly|beta|1\.[0-9][0-9]\.[0-9]" -> "$$CHANNEL"
 #![deny(warnings)]
 
 //! Linking to [foo@banana] and [`bar@banana!()`].
diff --git a/src/test/rustdoc-ui/intra-doc/unknown-disambiguator.stderr b/src/test/rustdoc-ui/intra-doc/unknown-disambiguator.stderr
index 94d6d461651..d280e6497e0 100644
--- a/src/test/rustdoc-ui/intra-doc/unknown-disambiguator.stderr
+++ b/src/test/rustdoc-ui/intra-doc/unknown-disambiguator.stderr
@@ -1,56 +1,56 @@
 error: unknown disambiguator `foo`
-  --> $DIR/unknown-disambiguator.rs:3:17
+  --> $DIR/unknown-disambiguator.rs:4:17
    |
 LL | //! Linking to [foo@banana] and [`bar@banana!()`].
    |                 ^^^
    |
 note: the lint level is defined here
-  --> $DIR/unknown-disambiguator.rs:1:9
+  --> $DIR/unknown-disambiguator.rs:2:9
    |
 LL | #![deny(warnings)]
    |         ^^^^^^^^
    = note: `#[deny(rustdoc::broken_intra_doc_links)]` implied by `#[deny(warnings)]`
-   = note: see https://doc.rust-lang.org/nightly/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
+   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
 
 error: unknown disambiguator `bar`
-  --> $DIR/unknown-disambiguator.rs:3:35
+  --> $DIR/unknown-disambiguator.rs:4:35
    |
 LL | //! Linking to [foo@banana] and [`bar@banana!()`].
    |                                   ^^^
    |
-   = note: see https://doc.rust-lang.org/nightly/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
+   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
 
 error: unknown disambiguator `foo`
-  --> $DIR/unknown-disambiguator.rs:9:34
+  --> $DIR/unknown-disambiguator.rs:10:34
    |
 LL | //! And with weird backticks: [``foo@hello``] [foo`@`hello].
    |                                  ^^^
    |
-   = note: see https://doc.rust-lang.org/nightly/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
+   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
 
 error: unknown disambiguator `foo`
-  --> $DIR/unknown-disambiguator.rs:9:48
+  --> $DIR/unknown-disambiguator.rs:10:48
    |
 LL | //! And with weird backticks: [``foo@hello``] [foo`@`hello].
    |                                                ^^^
    |
-   = note: see https://doc.rust-lang.org/nightly/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
+   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
 
 error: unknown disambiguator ``
-  --> $DIR/unknown-disambiguator.rs:6:31
+  --> $DIR/unknown-disambiguator.rs:7:31
    |
 LL | //! And to [no disambiguator](@nectarine) and [another](@apricot!()).
    |                               ^
    |
-   = note: see https://doc.rust-lang.org/nightly/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
+   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
 
 error: unknown disambiguator ``
-  --> $DIR/unknown-disambiguator.rs:6:57
+  --> $DIR/unknown-disambiguator.rs:7:57
    |
 LL | //! And to [no disambiguator](@nectarine) and [another](@apricot!()).
    |                                                         ^
    |
-   = note: see https://doc.rust-lang.org/nightly/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
+   = note: see https://doc.rust-lang.org/$CHANNEL/rustdoc/linking-to-items-by-name.html#namespaces-and-disambiguators for more info about disambiguators
 
 error: aborting due to 6 previous errors
 
diff --git a/src/test/rustdoc-ui/no-crate-level-doc-lint.rs b/src/test/rustdoc-ui/no-crate-level-doc-lint.rs
index 3939ec6827a..a186410acf4 100644
--- a/src/test/rustdoc-ui/no-crate-level-doc-lint.rs
+++ b/src/test/rustdoc-ui/no-crate-level-doc-lint.rs
@@ -1,4 +1,5 @@
 // error-pattern: no documentation found
+// normalize-stderr-test: "nightly|beta|1\.[0-9][0-9]\.[0-9]" -> "$$CHANNEL"
 #![deny(rustdoc::missing_crate_level_docs)]
 //^~ NOTE defined here
 
diff --git a/src/test/rustdoc-ui/no-crate-level-doc-lint.stderr b/src/test/rustdoc-ui/no-crate-level-doc-lint.stderr
index 55ead1a55cf..1a1f8085a1b 100644
--- a/src/test/rustdoc-ui/no-crate-level-doc-lint.stderr
+++ b/src/test/rustdoc-ui/no-crate-level-doc-lint.stderr
@@ -1,12 +1,12 @@
 error: no documentation found for this crate's top-level module
    |
 note: the lint level is defined here
-  --> $DIR/no-crate-level-doc-lint.rs:2:9
+  --> $DIR/no-crate-level-doc-lint.rs:3:9
    |
 LL | #![deny(rustdoc::missing_crate_level_docs)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = help: The following guide may be of use:
-           https://doc.rust-lang.org/nightly/rustdoc/how-to-write-documentation.html
+           https://doc.rust-lang.org/$CHANNEL/rustdoc/how-to-write-documentation.html
 
 error: aborting due to previous error