fix: Fix common settings loading when root is synthetic

**Problem**
The new common settings feature doesn't work when the root isn't created by the user.

**Solution**
This fixes common settings by calling `expandCommonSettingsPerBase(...)` on
the synthetic root's base first.

sbt-app/src/sbt-test/actions/cross-strict-aggregation-scala-3/build.sbt

@@ -1,5 +1,4 @@
 scalaVersion := "2.12.19"
-name := "root"
 
 lazy val core = project
   .settings(

sbt-app/src/sbt-test/dependency-management/parent-skip-publish/build.sbt

@@ -1,11 +1,9 @@
-ThisBuild / organization := "com.example"
-ThisBuild / ivyPaths := IvyPaths((ThisBuild / baseDirectory).value.toString, Some(((ThisBuild / baseDirectory).value / "ivy" / "cache").toString))
+organization := "com.example"
+ivyPaths := IvyPaths((ThisBuild / baseDirectory).value.toString, Some(((ThisBuild / baseDirectory).value / "ivy" / "cache").toString))
 
 name := "root"
 
 lazy val core = project
   .settings(
     name := "core",
-    // organization := "com.example",
-    ivyPaths := IvyPaths((ThisBuild / baseDirectory).value.toString, Some(((ThisBuild / baseDirectory).value / "ivy" / "cache").toString))
   )

sbt-app/src/sbt-test/project-matrix/custom/build.sbt

@@ -1,12 +1,11 @@
-ThisBuild / organization := "com.example"
-ThisBuild / version := "0.1.0-SNAPSHOT"
-ThisBuild / publishMavenStyle := true
-
-ThisBuild / ivyPaths := {
-  val base = (ThisBuild / baseDirectory).value
-  IvyPaths(base.toString, s"$base/ivy-cache")
+organization := "com.example"
+version := "0.1.0-SNAPSHOT"
+publishMavenStyle := true
+ivyPaths := {
+  val base = baseDirectory.value
+  val thisBuildBase = (ThisBuild / baseDirectory).value
+  IvyPaths(base.toString, s"$thisBuildBase/ivy-cache")
 }
-publish / skip := true
 
 lazy val config12 = ConfigAxis("Config1_2", "config1.2")
 lazy val config13 = ConfigAxis("Config1_3", "config1.3")
@@ -21,7 +20,6 @@ lazy val app = (projectMatrix in file("app"))
   .dependsOn(core)
   .settings(
     name := "app",
-    ivyPaths := (ThisBuild / ivyPaths).value
   )
   .customRow(
     scalaVersions = Seq(scala212, scala211),

sbt-app/src/sbt-test/project-matrix/java/build.sbt

@@ -1,12 +1,11 @@
-ThisBuild / organization := "com.example"
-ThisBuild / version := "0.1.0-SNAPSHOT"
-ThisBuild / publishMavenStyle := true
-
-ThisBuild / ivyPaths := {
-  val base = (ThisBuild / baseDirectory).value
-  IvyPaths(base.toString, s"$base/ivy-cache")
+organization := "com.example"
+version := "0.1.0-SNAPSHOT"
+publishMavenStyle := true
+ivyPaths := {
+  val base = baseDirectory.value
+  val thisBuildBase = (ThisBuild / baseDirectory).value
+  IvyPaths(base.toString, s"$thisBuildBase/ivy-cache")
 }
-publish / skip := true
 
 lazy val config12 = ConfigAxis("Config1_2", "-config1.2")
 lazy val config13 = ConfigAxis("Config1_3", "-config1.3")
@@ -16,7 +15,6 @@ lazy val scala212 = "2.12.10"
 lazy val app = (projectMatrix in file("app"))
   .settings(
     name := "app",
-    ivyPaths := (ThisBuild / ivyPaths).value
   )
   .customRow(
     scalaVersions = Seq(scala212),

sbt-app/src/sbt-test/project/common-settings-synthetic-root/baz/build.sbt

@@ -0,0 +1 @@
+organization := "com.example.baz"

sbt-app/src/sbt-test/project/common-settings-synthetic-root/build.sbt

@@ -0,0 +1,28 @@
+lazy val check = taskKey[Unit]("")
+
+def scala212 = "2.12.19"
+scalaVersion := scala212
+val o = "com.example"
+organization := o
+
+lazy val foo = project
+lazy val bar = project
+  .settings(
+    name := "bar",
+    organization := "com.example.bar",
+  )
+
+lazy val baz = project
+
+check := {
+  assert((foo / scalaVersion).value == scala212)
+  assert((bar / scalaVersion).value == scala212)
+  assert((baz / scalaVersion).value == scala212)
+
+  assert((foo / organization).value == o)
+  // Test that bar can override common setting in settings(...)
+  assert((bar / organization).value == "com.example.bar", s"unexpected bar / organization = {(bar / organization).value}")
+  // Test that baz/build.sbt bare settings get loaded
+  assert((baz / organization).value == "com.example.baz", s"unexpected baz/organization")
+}
+check / aggregate := false

sbt-app/src/sbt-test/project/common-settings-synthetic-root/test

@@ -0,0 +1 @@
+> check

sbt-app/src/sbt-test/project/common-settings/baz/build.sbt

@@ -0,0 +1 @@
+organization := "com.example.baz"

sbt-app/src/sbt-test/project/common-settings/build.sbt

@@ -0,0 +1,33 @@
+lazy val check = taskKey[Unit]("")
+
+def scala212 = "2.12.19"
+scalaVersion := scala212
+val o = "com.example"
+organization := o
+
+lazy val root = (project in file("."))
+  .aggregate(foo, bar, baz)
+
+lazy val foo = project
+lazy val bar = project
+  .settings(
+    name := "bar",
+    organization := "com.example.bar",
+  )
+
+lazy val baz = project
+
+check := {
+  assert((root / scalaVersion).value == scala212)
+  assert((foo / scalaVersion).value == scala212)
+  assert((bar / scalaVersion).value == scala212)
+  assert((baz / scalaVersion).value == scala212)
+
+  assert((root / organization).value == o)
+  assert((foo / organization).value == o)
+  // Test that bar can override common setting in settings(...)
+  assert((bar / organization).value == "com.example.bar")
+  // Test that baz/build.sbt bare settings get loaded
+  assert((baz / organization).value == "com.example.baz")
+}
+check / aggregate := false

sbt-app/src/sbt-test/project/common-settings/test

@@ -0,0 +1 @@
+> check

sbt-app/src/sbt-test/reporter/nowarn/build.sbt

@@ -1,13 +1,19 @@
-ThisBuild / scalaVersion := "2.12.17"
+scalaVersion := "2.12.19"
 
 lazy val sub1 = project
 
 lazy val sub2 = project
 
 val assertNoWarning = taskKey[Unit]("checks warning *is not* emitted")
-
 val assertWarning = taskKey[Unit]("checks warning *is* emitted")
 
+lazy val root = (project in file("."))
+  .aggregate(sub1, sub2)
+  .settings(
+    assertWarning := check(true).value,
+    assertNoWarning := check(false).value,
+  )
+
 def check(expectation: Boolean) = Def.task[Unit] {
   val lastLog: File = BuiltinCommands.lastLogFile(state.value).get
   val last: String = IO.read(lastLog)
@@ -20,7 +26,3 @@ def check(expectation: Boolean) = Def.task[Unit] {
     IO.write(lastLog, "") // clear the backing log for for 'last'.
   }
 }
-
-assertWarning := check(true).value
-
-assertNoWarning := check(false).value