Add support for legacy -doc-source-url option

Author: pikinier20

scaladoc/src/dotty/tools/scaladoc/Scaladoc.scala

@@ -169,6 +169,7 @@ object Scaladoc:
           CommentSyntax.default
         }
       }
+      val legacySourceLinkList = if legacySourceLink.get.nonEmpty then List(legacySourceLink.get) else Nil
       val externalMappings =
         externalDocumentationMappings.get.flatMap( s =>
             ExternalDocLink.parse(s).fold(left => {
@@ -208,7 +209,7 @@ object Scaladoc:
         projectLogo.nonDefault,
         projectFooter.nonDefault,
         parseSyntax,
-        sourceLinks.get,
+        sourceLinks.get ++ legacySourceLinkList,
         revision.nonDefault,
         externalMappings,
         socialLinksParsed,

scaladoc/src/dotty/tools/scaladoc/ScaladocSettings.scala

@@ -41,6 +41,9 @@ class ScaladocSettings extends SettingGroup with AllScalaSettings:
   val sourceLinks: Setting[List[String]] =
     MultiStringSetting("-source-links", "sources", SourceLinks.usage)
 
+  val legacySourceLink: Setting[String] =
+    StringSetting("-doc-source-url", "sources", "Legacy option from Scala 2. Use -source-links instead.", "")
+
   val syntax: Setting[String] =
     StringSetting("-comment-syntax", "syntax", "Syntax of the comment used", "")
 
@@ -124,4 +127,4 @@ class ScaladocSettings extends SettingGroup with AllScalaSettings:
     StringSetting("-scastie-configuration", "Scastie configuration", "Additional configuration passed to Scastie in code snippets", "")
 
   def scaladocSpecificSettings: Set[Setting[_]] =
-    Set(sourceLinks, syntax, revision, externalDocumentationMappings, socialLinks, skipById, skipByRegex, deprecatedSkipPackages, docRootContent, snippetCompiler, generateInkuire, scastieConfiguration)
+    Set(sourceLinks, legacySourceLink, syntax, revision, externalDocumentationMappings, socialLinks, skipById, skipByRegex, deprecatedSkipPackages, docRootContent, snippetCompiler, generateInkuire, scastieConfiguration)