Add --host option to PreviewOptions

This retains the `localhost` default host name for the preview server,
but allows the user to override it by providing `--host`.

We’re only supporting the long `--host` option because `-h` already
means `--help`.

Author: tomstuart

Sources/SwiftDocCUtilities/ArgumentParsing/ActionExtensions/PreviewAction+CommandInitialization.swift

@@ -24,7 +24,7 @@ extension PreviewAction {
     {
         // Initialize the `PreviewAction` from the options provided by the `Preview` command
         try self.init(
-            host: "localhost",
+            host: previewOptions.host,
             port: previewOptions.port,
             createConvertAction: {
                 try ConvertAction(

Sources/SwiftDocCUtilities/ArgumentParsing/Options/PreviewOptions.swift

@@ -17,6 +17,16 @@ import Foundation
 public struct PreviewOptions: ParsableArguments {
     public init() { }
 
+    /// The host name to use for the preview web server.
+    ///
+    /// Defaults to `localhost`.
+    @Option(
+        name: .long,
+        help: ArgumentHelp(
+            "Host name to use for the preview web server.",
+            valueName: "host-name"))
+    public var host: String = "localhost"
+
     /// The port number to use for the preview web server.
     ///
     /// Defaults to `8080`.

Sources/SwiftDocCUtilities/ArgumentParsing/Subcommands/Preview.swift

@@ -23,9 +23,9 @@ extension Docc {
         public static var configuration = CommandConfiguration(
             abstract: "Convert documentation inputs and preview the documentation output.",
             usage: """
-            docc preview [<catalog-path>] [--port <port-number>] [--additional-symbol-graph-dir <symbol-graph-dir>]
-            docc preview [<catalog-path>] [--port <port-number>] [--additional-symbol-graph-dir <symbol-graph-dir>] [--output-dir <output-dir>]
-            docc preview [<catalog-path>] [--port <port-number>] [--additional-symbol-graph-dir <symbol-graph-dir>] [--output-dir <output-dir>] [<availability-options>] [<diagnostic-options>] [<source-repository-options>] [<hosting-options>] [<info-plist-fallbacks>] [<feature-flags>] [<other-options>]
+            docc preview [<catalog-path>] [--host <host-name>] [--port <port-number>] [--additional-symbol-graph-dir <symbol-graph-dir>]
+            docc preview [<catalog-path>] [--host <host-name>] [--port <port-number>] [--additional-symbol-graph-dir <symbol-graph-dir>] [--output-dir <output-dir>]
+            docc preview [<catalog-path>] [--host <host-name>] [--port <port-number>] [--additional-symbol-graph-dir <symbol-graph-dir>] [--output-dir <output-dir>] [<availability-options>] [<diagnostic-options>] [<source-repository-options>] [<hosting-options>] [<info-plist-fallbacks>] [<feature-flags>] [<other-options>]
             """,
             discussion: """
             The 'preview' command extends the 'convert' command by running a preview server and monitoring the documentation input for modifications to rebuild the documentation.