Add whitespaces in Show of scoped keys

```
Provided by:
    ProjectRef(uri("...."), "root") / Test / test
Dependencies:
    Test / executeTests
    Test / test / streams
    Test / state
    Test / test / testResultLogger
```

main-settings/src/main/scala/sbt/Def.scala

@@ -75,7 +75,7 @@ object Def extends Init[Scope] with TaskMacroExtra {
   private[sbt] def displayRelative(current: ProjectRef,
                                    project: Reference,
                                    trailingSlash: Boolean): String = {
-    val trailing = if (trailingSlash) "/" else ""
+    val trailing = if (trailingSlash) " /" else ""
     project match {
       case BuildRef(current.build)      => "ThisBuild" + trailing
       case `current`                    => ""
@@ -86,9 +86,9 @@ object Def extends Init[Scope] with TaskMacroExtra {
 
   def displayBuildRelative(currentBuild: URI, multi: Boolean, project: Reference): String =
     project match {
-      case BuildRef(`currentBuild`)      => "ThisBuild/"
-      case ProjectRef(`currentBuild`, x) => x + "/"
-      case _                             => Reference.display(project) + "/"
+      case BuildRef(`currentBuild`)      => "ThisBuild /"
+      case ProjectRef(`currentBuild`, x) => x + " /"
+      case _                             => Reference.display(project) + " /"
     }
 
   def displayFull(scoped: ScopedKey[_]): String = displayFull(scoped, None)

main-settings/src/main/scala/sbt/Reference.scala

@@ -91,7 +91,7 @@ object Reference {
       case LocalRootProject    => "{<this>}<root>"
       case LocalProject(id)    => "{<this>}" + id
       case RootProject(uri)    => "{" + uri + " }<root>"
-      case ProjectRef(uri, id) => s"""ProjectRef(uri("$uri"),"$id")"""
+      case ProjectRef(uri, id) => s"""ProjectRef(uri("$uri"), "$id")"""
     }
 
   def buildURI(ref: ResolvedReference): URI = ref match {

main-settings/src/main/scala/sbt/Scope.scala

@@ -123,7 +123,7 @@ object Scope {
       case BuildRef(uri) => BuildRef(resolveBuild(current, uri))
     }
 
-  def display(config: ConfigKey): String = guessConfigIdent(config.name) + "/"
+  def display(config: ConfigKey): String = guessConfigIdent(config.name) + " /"
 
   private[sbt] val configIdents: Map[String, String] =
     Map(
@@ -176,16 +176,24 @@ object Scope {
                     mask: ScopeMask,
                     showZeroConfig: Boolean): String = {
     import scope.{ project, config, task, extra }
-    val zeroConfig = if (showZeroConfig) "Zero/" else ""
+    val zeroConfig = if (showZeroConfig) "Zero /" else ""
     val configPrefix = config.foldStrict(display, zeroConfig, "./")
-    val taskPrefix = task.foldStrict(_.label + "/", "", "./")
+    val taskPrefix = task.foldStrict(_.label + " /", "", "./")
     val extras = extra.foldStrict(_.entries.map(_.toString).toList, Nil, Nil)
     val postfix = if (extras.isEmpty) "" else extras.mkString("(", ", ", ")")
-    if (scope == GlobalScope) "Global/" + sep + postfix
+    if (scope == GlobalScope) "Global / " + sep + postfix
     else
-      mask.concatShow(projectPrefix(project, showProject), configPrefix, taskPrefix, sep, postfix)
+      mask.concatShow(appendSpace(projectPrefix(project, showProject)),
+                      appendSpace(configPrefix),
+                      appendSpace(taskPrefix),
+                      sep,
+                      postfix)
   }
 
+  private[sbt] def appendSpace(s: String): String =
+    if (s == "") ""
+    else s + " "
+
   // sbt 0.12 style
   def display012StyleMasked(scope: Scope,
                             sep: String,
@@ -196,7 +204,7 @@ object Scope {
     val taskPrefix = task.foldStrict(_.label + "::", "", ".::")
     val extras = extra.foldStrict(_.entries.map(_.toString).toList, Nil, Nil)
     val postfix = if (extras.isEmpty) "" else extras.mkString("(", ", ", ")")
-    mask.concatShow(projectPrefix012Style(project, showProject),
+    mask.concatShow(projectPrefix012Style(project, showProject012Style),
                     configPrefix,
                     taskPrefix,
                     sep,
@@ -211,13 +219,15 @@ object Scope {
 
   def projectPrefix(project: ScopeAxis[Reference],
                     show: Reference => String = showProject): String =
-    project.foldStrict(show, "Zero/", "./")
+    project.foldStrict(show, "Zero /", "./")
 
   def projectPrefix012Style(project: ScopeAxis[Reference],
                             show: Reference => String = showProject): String =
     project.foldStrict(show, "*/", "./")
 
-  def showProject = (ref: Reference) => Reference.display(ref) + "/"
+  def showProject = (ref: Reference) => Reference.display(ref) + " /"
+
+  def showProject012Style = (ref: Reference) => Reference.display(ref) + "/"
 
   def transformTaskName(s: String) = {
     val parts = s.split("-+")

main/src/test/scala/sbt/internal/server/SettingQueryTest.scala

@@ -202,7 +202,7 @@ object SettingQueryTest extends org.specs2.mutable.Specification {
 
     "scalaVersion" in qko("Not a valid project ID: scalaVersion\\nscalaVersion\\n            ^")
     "t/scalacOptions" in qko(
-      s"""Key ProjectRef(uri(\\"$baseUri\\"),\\"t\\")/Compile/scalacOptions is a task, can only query settings""")
+      s"""Key ProjectRef(uri(\\"$baseUri\\"), \\"t\\") / Compile / scalacOptions is a task, can only query settings""")
     "t/fooo" in qko(
       "Expected ':' (if selecting a configuration)\\nNot a valid key: fooo (similar: fork)\\nt/fooo\\n      ^")
   }

sbt/src/sbt-test/project/unified/build.sbt

@@ -21,29 +21,29 @@ lazy val root = (project in file("."))
 Description:
 \tExecutes all tests.
 Provided by:
-\tProjectRef(uri("${baseDirectory.value.toURI}"),"root")/Test/test
+\tProjectRef(uri("${baseDirectory.value.toURI}"), "root") / Test / test
 Defined at:
 \t(sbt.Defaults.testTasks) Defaults.scala:670
 Dependencies:
-\tTest/executeTests
-\tTest/test/streams
-\tTest/state
-\tTest/test/testResultLogger
+\tTest / executeTests
+\tTest / test / streams
+\tTest / state
+\tTest / test / testResultLogger
 Delegates:
-\tTest/test
-\tRuntime/test
-\tCompile/test
+\tTest / test
+\tRuntime / test
+\tCompile / test
 \ttest
-\tThisBuild/Test/test
-\tThisBuild/Runtime/test
-\tThisBuild/Compile/test
-\tThisBuild/test
-\tZero/Test/test
-\tZero/Runtime/test
-\tZero/Compile/test
-\tGlobal/test
+\tThisBuild / Test / test
+\tThisBuild / Runtime / test
+\tThisBuild / Compile / test
+\tThisBuild / test
+\tZero / Test / test
+\tZero / Runtime / test
+\tZero / Compile / test
+\tGlobal / test
 Related:
-\tprojA/Test/test"""
+\tprojA / Test / test"""
 
         if (processText(actual) == processText(expected)) ()
         else {
@@ -52,7 +52,14 @@ $actual
 
 expected:
 $expected
-""")
+
+diff:
+""" +
+(
+  processText(actual)
+    zip processText(expected)
+    filter { case ( a, b) => a != b }
+))
         }
         s.log.info(actual)
         s