Use projectInfoVersion for paths of generated docs (akka#1759)

build.sbt

@@ -276,12 +276,12 @@ lazy val docs = project
     whitesourceIgnore := true,
     makeSite := makeSite.dependsOn(LocalRootProject / ScalaUnidoc / doc).value,
     previewPath := (Paradox / siteSubdirName).value,
-    Preprocess / siteSubdirName := s"api/alpakka/${if (isSnapshot.value) "snapshot" else version.value}",
+    Preprocess / siteSubdirName := s"api/alpakka/${projectInfoVersion.value}",
     Preprocess / sourceDirectory := (LocalRootProject / ScalaUnidoc / unidoc / target).value,
     Preprocess / preprocessRules := Seq(
         ("\\.java\\.scala".r, _ => ".java")
       ),
-    Paradox / siteSubdirName := s"docs/alpakka/${if (isSnapshot.value) "snapshot" else version.value}",
+    Paradox / siteSubdirName := s"docs/alpakka/${projectInfoVersion.value}",
     paradoxProperties ++= Map(
         "akka.version" -> Dependencies.AkkaVersion,
         "akka-http.version" -> Dependencies.AkkaHttpVersion,
@@ -314,7 +314,7 @@ lazy val docs = project
         "javadoc.org.eclipse.paho.client.mqttv3.base_url" -> "https://www.eclipse.org/paho/files/javadoc/",
         "javadoc.org.bson.codecs.configuration.base_url" -> "https://mongodb.github.io/mongo-java-driver/3.7/javadoc/",
         "scaladoc.scala.base_url" -> s"https://www.scala-lang.org/api/${scalaBinaryVersion.value}.x/",
-        "scaladoc.akka.stream.alpakka.base_url" -> s"/api/alpakka/${if (isSnapshot.value) "snapshot" else version.value}/"
+        "scaladoc.akka.stream.alpakka.base_url" -> s"/${(Preprocess / siteSubdirName).value}/"
       ),
     paradoxGroups := Map("Language" -> Seq("Java", "Scala")),
     resolvers += Resolver.jcenterRepo,