Warn if legacy cache location ~/.coursier/cache is found (#222)

modules/lm-coursier/src/main/scala/lmcoursier/CoursierConfiguration.scala

@@ -1,6 +1,7 @@
 package lmcoursier
 
 import java.io.File
+import java.util.concurrent.atomic.AtomicBoolean
 
 import dataclass.data
 import coursier.cache.CacheDefaults
@@ -82,6 +83,12 @@ import scala.concurrent.duration.Duration
 }
 
 object CoursierConfiguration {
+
+  private var checkedLegacyCache = new AtomicBoolean
+  def checkLegacyCache(): Unit =
+    if (!checkedLegacyCache.getAndSet(true))
+      coursier.cache.CacheDefaults.warnLegacyCacheLocation()
+
   def apply(
     log: Logger,
     resolvers: Vector[Resolver],

modules/lm-coursier/src/main/scala/lmcoursier/CoursierDependencyResolution.scala

@@ -15,6 +15,8 @@ import sbt.util.Logger
 
 class CoursierDependencyResolution(conf: CoursierConfiguration) extends DependencyResolutionInterface {
 
+  lmcoursier.CoursierConfiguration.checkLegacyCache()
+
   /*
    * Based on earlier implementations by @leonardehrenfried (https://github.com/sbt/librarymanagement/pull/190)
    * and @andreaTP (https://github.com/sbt/librarymanagement/pull/270), then adapted to the code from the former

modules/sbt-coursier-shared/src/main/scala/coursier/sbtcoursiershared/SbtCoursierShared.scala

@@ -14,6 +14,8 @@ import sbt.librarymanagement.{ModuleID, Resolver, URLRepository}
 
 object SbtCoursierShared extends AutoPlugin {
 
+  lmcoursier.CoursierConfiguration.checkLegacyCache()
+
   override def trigger = allRequirements
 
   override def requires = sbt.plugins.JvmPlugin