Move markdown formatting to the contributor guide

Author: ehuss

contributor-guide/src/SUMMARY.md

@@ -8,7 +8,7 @@
     - [mdbook-spec](tooling/mdbook-spec.md)
 - [Tests]()
 - [Formatting](formatting/index.md)
-    - [Markdown]()
+    - [Markdown](formatting/markdown.md)
     - [Admonitions]()
 - [Language rules]()
     - [rustc test annotations]()

contributor-guide/src/formatting/markdown.md

@@ -0,0 +1,45 @@
+# Markdown
+
+There are automated checks for some of these rules. Run [`cargo xtask style-check`] to run them locally.
+
+## Formatting style
+
+- Use [ATX-style headings][atx] (not Setext) with [sentence case].
+- Do not use tabs, only spaces.
+- Files must end with a newline.
+- Lines must not end with spaces. Double spaces have semantic meaning, but can be invisible. Use a trailing backslash if you need a hard line break.
+- If possible, avoid double blank lines.
+- Do not wrap long lines. This helps with reviewing diffs of the source.
+- Use [smart punctuation] instead of Unicode characters. For example, use `---` for em-dash instead of the Unicode character. Characters like em-dash can be difficult to see in a fixed-width editor, and some editors may not have easy methods to enter such characters.
+- See the [admonitions chapter] for formatting callouts such as notes, edition differences, and warnings.
+
+## Code blocks
+
+- Do not use indented code blocks; use 3+ backticks code blocks instead.
+- Code blocks should have an explicit language tag.
+
+## Links
+
+See the [links chapter] for more information about linking.
+
+- Links to other chapters should be relative with the `.md` extension.
+- Links to other rust-lang books that are published with the Reference should also be relative so that the linkchecker can validate them. See [outside book links].
+- Links to the standard library should use rustdoc-style links described in [standard library links].
+- The use of reference links is preferred, with shortcuts if appropriate. Place the sorted link reference definitions at the bottom of the file or at the bottom of a section if there are an unusually large number of links that are specific to the section.
+
+    ```markdown
+    Example of shortcut link: [enumerations]
+    Example of reference link with label: [block expression][block]
+
+    [block]: expressions/block-expr.md
+    [enumerations]: types/enum.md
+    ```
+
+[`cargo xtask style-check`]: ../tests.md#style-checks
+[admonitions chapter]: admonitions.md
+[atx]: https://spec.commonmark.org/0.31.2/#atx-headings
+[links chapter]: ../links.md
+[outside book links]: ../links.md#outside-book-links
+[sentence case]: https://apastyle.apa.org/style-grammar-guidelines/capitalization/sentence-case
+[smart punctuation]: https://rust-lang.github.io/mdBook/format/markdown.html#smart-punctuation
+[standard library links]: ../links.md#standard-library-links

docs/authoring.md

@@ -4,37 +4,6 @@ This document serves as a guide for editors and reviewers. Some conventions and
 
 [introduction]: ../src/introduction.md
 
-## Markdown formatting
-
-* Use [ATX-style headings][atx] (not Setext) with [sentence case].
-* Do not use tabs, only spaces.
-* Files must end with a newline.
-* Lines must not end with spaces. Double spaces have semantic meaning, but can be invisible. Use a trailing backslash if you need a hard line break.
-* If possible, avoid double blank lines.
-* Do not use indented code blocks; use 3+ backticks code blocks instead.
-* Code blocks should have an explicit language tag.
-* Do not wrap long lines. This helps with reviewing diffs of the source.
-* Use [smart punctuation] instead of Unicode characters. For example, use `---` for em-dash instead of the Unicode character. Characters like em-dash can be difficult to see in a fixed-width editor, and some editors may not have easy methods to enter such characters.
-* Links should be relative with the `.md` extension. Links to other rust-lang books that are published with the reference should also be relative so that the linkchecker can validate them.
-* Links to the standard library should use rustdoc-style links described in [Standard library links](#standard-library-links).
-* The use of reference links is preferred, with shortcuts if appropriate. Place the sorted link reference definitions at the bottom of the file, or at the bottom of a section if there are an unusually large number of links that are specific to the section.
-
-    ```markdown
-    Example of shortcut link: [enumerations]
-    Example of reference link with label: [block expression][block]
-
-    [block]: expressions/block-expr.md
-    [enumerations]: types/enum.md
-    ```
-* See the [Conventions] section for formatting callouts such as notes, edition differences, and warnings.
-
-There are automated checks for some of these rules. Run `cargo xtask style-check` to run them locally.
-
-[atx]: https://spec.commonmark.org/0.31.2/#atx-headings
-[conventions]: ../src/introduction.md#conventions
-[sentence case]: https://apastyle.apa.org/style-grammar-guidelines/capitalization/sentence-case
-[smart punctuation]: https://rust-lang.github.io/mdBook/format/markdown.html#smart-punctuation
-
 ### Code examples
 
 Code examples should use code blocks with triple backticks. The language should always be specified (such as `rust`).