improve extendsFromFlattened utility

src/main/kotlin/org/incendo/cloudbuildlogic/util/configurations.kt

@@ -2,16 +2,28 @@ package org.incendo.cloudbuildlogic.util
 
 import org.gradle.api.NamedDomainObjectProvider
 import org.gradle.api.artifacts.Configuration
+import org.gradle.api.artifacts.component.ProjectComponentIdentifier
 import org.gradle.api.artifacts.dsl.DependencyHandler
+import org.gradle.kotlin.dsl.project
 import org.incendo.cloudbuildlogic.coordinates
 import org.incendo.cloudbuildlogic.moduleComponentId
 
+/**
+ * When [includeProjectDependencies] is false, project dependencies will be excluded,
+ * but their transitive dependencies will not be.
+ */
 fun Configuration.extendsFromFlattened(
     other: NamedDomainObjectProvider<Configuration>,
     dependencyHandler: DependencyHandler,
+    includeProjectDependencies: Boolean = false,
 ) {
     defaultDependencies {
         for (artifact in other.get().incoming.artifacts.artifacts) {
+            if (includeProjectDependencies && artifact.id.componentIdentifier is ProjectComponentIdentifier) {
+                val projectId = artifact.id.componentIdentifier as ProjectComponentIdentifier
+                add(dependencyHandler.project(projectId.projectPath))
+                continue
+            }
             val id = artifact.moduleComponentId() ?: continue
             add(dependencyHandler.create(coordinates(id)))
         }