chore: documentation folder should be driven by variable (#386)

Cleans up all references to the `”documentation”` and
`”tutorial`”’ subpaths to be driven by the property
in `NodeURLGenerator`.

Author: ethan-kusters

Sources/SwiftDocC/Infrastructure/Link Resolution/PathHierarchy.swift

@@ -434,8 +434,8 @@ struct PathHierarchy {
     /// - Returns: The node to start the relative search relative to.
     private func findRoot(parentID: ResolvedIdentifier?, remaining: inout ArraySlice<PathComponent>, isAbsolute: Bool, onlyFindSymbols: Bool) throws -> Node {
         // If the first path component is "tutorials" or "documentation" then that
-        let isKnownTutorialPath = remaining.first!.full == "tutorials"
-        let isKnownDocumentationPath = remaining.first!.full == "documentation"
+        let isKnownTutorialPath = remaining.first!.full == NodeURLGenerator.Path.tutorialsFolderName
+        let isKnownDocumentationPath = remaining.first!.full == NodeURLGenerator.Path.documentationFolderName
         if isKnownDocumentationPath || isKnownTutorialPath {
             // Drop that component since it isn't represented in the path hierarchy.
             remaining.removeFirst()
@@ -626,7 +626,9 @@ extension PathHierarchy {
     static func parse(path: String) -> (components: [PathComponent], isAbsolute: Bool) {
         guard !path.isEmpty else { return ([], true) }
         var components = path.split(separator: "/", omittingEmptySubsequences: true)
-        let isAbsolute = path.first == "/" || components.first == "documentation" || components.first == "tutorials"
+        let isAbsolute = path.first == "/"
+            || String(components.first ?? "") == NodeURLGenerator.Path.documentationFolderName
+            || String(components.first ?? "") == NodeURLGenerator.Path.tutorialsFolderName
 
         if let hashIndex = components.last?.firstIndex(of: "#") {
             let last = components.removeLast()

Sources/SwiftDocC/Infrastructure/NodeURLGenerator.swift

@@ -165,7 +165,10 @@ public struct NodeURLGenerator {
     public func urlForReference(_ reference: ResolvedTopicReference, fileSafePath safePath: String) -> URL {
         if safePath.isEmpty {
             // Return the root path for the conversion: /documentation.json
-            return baseURL.appendingPathComponent("documentation", isDirectory: false)
+            return baseURL.appendingPathComponent(
+                NodeURLGenerator.Path.documentationFolderName,
+                isDirectory: false
+            )
         } else {
             let url = baseURL.appendingPathComponent(safePath, isDirectory: false)
             return url.withFragment(reference.url.fragment)