Fix links in Mentioned In section

Author: d-ronnqvist

Sources/DocCHTML/MarkdownRenderer.swift

@@ -248,7 +248,7 @@ package struct MarkdownRenderer<Provider: LinkProvider> {
         )
     }
 
-    func path(to other: URL) -> String {
+    package func path(to other: URL) -> String {
         let from = path
         let to   = other
 

Sources/SwiftDocC/Model/Rendering/HTML/HTMLRenderer.swift

@@ -451,9 +451,16 @@ struct HTMLRenderer {
             let mentions = context.articleSymbolMentions.articlesMentioning(reference)
             if !mentions.isEmpty {
                 articleElement.addChildren(
+                    // FIXME: Create a dedicated MarkdownRenderer method for the "Mentioned In" section
                     renderer.selfReferencingSection(named: "Mentioned In", content: [
                         .element(named: "ul", children: mentions.compactMap { reference in
-                            context.documentationCache[reference].map { .element(named: "li", children: [.text($0.name.description)]) }
+                            context.documentationCache[reference].map {
+                                .element(named: "li", children: [
+                                    .element(named: "a", children: [.text($0.name.description)], attributes: [
+                                        "href": renderer.path(to: $0.reference.url) + "/index.html"
+                                    ])
+                                ])
+                            }
                         })
                     ])
                 )

Tests/SwiftDocCUtilitiesTests/FileWritingHTMLContentConsumerTests.swift

@@ -254,7 +254,9 @@ final class FileWritingHTMLContentConsumerTests: XCTestCase {
         </section>
         <h2>Mentioned In</h2>
         <ul>
-            <li>Some article</li>
+            <li>
+                <a href="../somearticle/index.html">Some article</a>
+            </li>
         </ul>
         <h2>Topics</h2>
         <h3>Instance Methods</h3>