refactor(sbt): Factor code out of checkConfiguredSbtVersions()

Do less in the function to make it more generally useful. This also
makes more clear where the version is configured, i.e. in the build
itself, and not e.g in ORT configuration. Adjust related variable names
and log statements accordingly.

Signed-off-by: Sebastian Schuberth <sebastian@doubleopen.org>

plugins/package-managers/sbt/src/main/kotlin/Sbt.kt

@@ -22,6 +22,7 @@ package org.ossreviewtoolkit.plugins.packagemanagers.sbt
 import java.io.File
 import java.nio.file.StandardCopyOption
 import java.util.Properties
+import java.util.SortedSet
 
 import kotlin.io.path.moveTo
 
@@ -34,13 +35,17 @@ import org.ossreviewtoolkit.model.config.RepositoryConfiguration
 import org.ossreviewtoolkit.plugins.packagemanagers.maven.Maven
 import org.ossreviewtoolkit.utils.common.CommandLineTool
 import org.ossreviewtoolkit.utils.common.Os
-import org.ossreviewtoolkit.utils.common.alsoIfNull
 import org.ossreviewtoolkit.utils.common.getCommonParentFile
 import org.ossreviewtoolkit.utils.common.searchUpwardsForSubdirectory
 import org.ossreviewtoolkit.utils.common.suppressInput
 
 import org.semver4j.Semver
 
+// We need at least sbt version 0.13.0 to be able to use "makePom" instead of the deprecated hyphenated
+// form "make-pom" and to support declaring Maven-style repositories, see
+// http://www.scala-sbt.org/0.13/docs/Publishing.html#Modifying+the+generated+POM.
+const val LOWEST_SUPPORTED_SBT_VERSION = "0.13.0"
+
 /**
  * The [SBT](https://www.scala-sbt.org/) package manager for Scala.
  */
@@ -70,7 +75,22 @@ class Sbt(
 
         logger.info { "Determined '$workingDir' as the $managerName project root directory." }
 
-        checkConfiguredSbtVersions(workingDir)
+        val sbtVersions = getBuildSbtVersions(workingDir)
+        when {
+            sbtVersions.isEmpty() ->
+                logger.info { "The build does not configure any $managerName version to be used." }
+
+            sbtVersions.size == 1 ->
+                logger.info { "The build configures $managerName version ${sbtVersions.first()} to be used." }
+
+            else ->
+                logger.warn { "The build configures multiple different $managerName versions to be used: $sbtVersions" }
+        }
+
+        val lowestSbtVersion = sbtVersions.firstOrNull()
+        require(lowestSbtVersion?.isLowerThan(Semver(LOWEST_SUPPORTED_SBT_VERSION)) != true) {
+            "Build $managerName version $lowestSbtVersion is lower than version $LOWEST_SUPPORTED_SBT_VERSION."
+        }
 
         fun runSbt(vararg command: String) =
             suppressInput {
@@ -113,7 +133,7 @@ class Sbt(
         }
     }
 
-    private fun checkConfiguredSbtVersions(workingDir: File): Semver? {
+    private fun getBuildSbtVersions(workingDir: File): SortedSet<Semver> {
         // Determine the SBT version(s) being used.
         val propertiesFiles = workingDir.walkBottomUp().filterTo(mutableListOf()) {
             it.isFile && it.name == "build.properties"
@@ -127,27 +147,7 @@ class Sbt(
             props.getProperty("sbt.version")?.let { versions += Semver(it) }
         }
 
-        val lowestConfiguredSbtVersion = versions.firstOrNull().alsoIfNull {
-            logger.warn { "No $managerName version configured in any of: ${propertiesFiles.joinToString()}" }
-        }
-
-        if (versions.size == 1) {
-            logger.info { "Configured $managerName version: $lowestConfiguredSbtVersion" }
-        } else {
-            logger.warn { "Different $managerName versions found: ${versions.joinToString()}" }
-        }
-
-        // We need at least sbt version 0.13.0 to be able to use "makePom" instead of the deprecated hyphenated
-        // form "make-pom" and to support declaring Maven-style repositories, see
-        // http://www.scala-sbt.org/0.13/docs/Publishing.html#Modifying+the+generated+POM.
-        val lowestSupportedSbtVersion = Semver("0.13.0")
-
-        require(lowestConfiguredSbtVersion?.isLowerThan(lowestSupportedSbtVersion) != true) {
-            "Configured $managerName version $lowestConfiguredSbtVersion is lower than version " +
-                "$lowestSupportedSbtVersion."
-        }
-
-        return lowestConfiguredSbtVersion
+        return versions
     }
 
     override fun resolveDependencies(definitionFiles: List<File>, labels: Map<String, String>) =