rl-next: Use markdown frontmatter syntax

The old syntax is still supported, as long as you don't use a {
in the description - the reason to migrate.

doc/manual/rl-next/hash-format-nix32.md

@@ -1,6 +1,7 @@
+---
 synopsis: Rename hash format `base32` to `nix32`
-prs: #9452
-description: {
+prs: 9452
+---
 
 Hash format `base32` was renamed to `nix32` since it used a special nix-specific character set for 
 [Base32](https://en.wikipedia.org/wiki/Base32).

doc/manual/rl-next/mounted-ssh-store.md

@@ -1,9 +1,8 @@
+---
 synopsis: Mounted SSH Store
-issues: #7890
-prs: #7912
-description: {
+issues: 7890
+prs: 7912
+---
 
 Introduced the store [`mounted-ssh-ng://`](@docroot@/command-ref/new-cli/nix3-help-stores.md).
 This store allows full access to a Nix store on a remote machine and additionally requires that the store be mounted in the local filesystem.
-
-}

doc/manual/rl-next/nix-config-show.md

@@ -1,8 +1,7 @@
-synopsis: `nix config show`
-issues: #7672
-prs: #9477
-description: {
+---
+synopsis: Rename to `nix config show`
+issues: 7672
+prs: 9477
+---
 
 `nix show-config` was renamed to `nix config show`, and `nix doctor` was renamed to `nix config check`, to be more consistent with the rest of the command-line interface.
-
-}

doc/manual/rl-next/nix-env-json-drv-path.md

@@ -1,9 +1,6 @@
+---
 synopsis: Fix `nix-env --query --drv-path --json`
-prs: #9257
-description: {
+prs: 9257
+---
 
 Fixed a bug where `nix-env --query` ignored `--drv-path` when `--json` was set.
-
-}
-
-

doc/manual/rl-next/nix-hash-convert.md

@@ -1,6 +1,7 @@
+---
 synopsis: Add `nix hash convert`
-prs: #9452
-description: {
+prs: 9452
+---
 
 New [`nix hash convert`](https://github.com/NixOS/nix/issues/8876) sub command with a fast track
 to stabilization! Examples:
@@ -44,4 +45,3 @@ The following commands are still available but will emit a deprecation warning.
 - `nix hash to-base64 $hash1 $hash2`: Use `nix hash convert --to base64 $hash1 $hash2` instead.
 - `nix hash to-sri $hash1 $hash2`: : Use `nix hash convert --to sri $hash1 $hash2`
   or even just `nix hash convert $hash1 $hash2` instead.
-}

doc/manual/rl-next/source-positions-in-errors.md

@@ -1,7 +1,8 @@
+---
 synopsis: Source locations are printed more consistently in errors
-issues: #561
-prs: #9555
-description: {
+issues: 561
+prs: 9555
+---
 
 Source location information is now included in error messages more
 consistently. Given this code:
@@ -39,5 +40,3 @@ error:
 
        error: value is a set while a string was expected
 ```
-
-}

doc/manual/src/contributing/hacking.md

@@ -257,17 +257,16 @@ User-visible changes should come with a release note.
 Here's what a complete entry looks like. The file name is not incorporated in the document.
 
 ```
+---
 synopsis: Basically a title
-issues: #1234
-prs: #1238
-description: {
+issues: 1234
+prs: 1238
+---
 
 Here's one or more paragraphs that describe the change.
 
 - It's markdown
 - Add references to the manual using @docroot@
-
-}
 ```
 
 Significant changes should add the following header, which moves them to the top.