Allow to manually add things in the classpath of launched apps

cli/src/main/scala-2.11/coursier/cli/Helper.scala

@@ -75,6 +75,7 @@ object Util {
 class Helper(
   common: CommonOptions,
   rawDependencies: Seq[String],
+  extraJars: Seq[File] = Nil,
   printResultStdout: Boolean = false,
   ignoreErrors: Boolean = false,
   isolated: IsolatedLoaderOptions = IsolatedLoaderOptions(),
@@ -648,7 +649,7 @@ class Helper(
   }
 
   lazy val loader = new URLClassLoader(
-    filteredFiles.map(_.toURI.toURL).toArray,
+    (filteredFiles ++ extraJars).map(_.toURI.toURL).toArray,
     parentLoader
   )
 

cli/src/main/scala-2.11/coursier/cli/Launch.scala

@@ -1,6 +1,7 @@
 package coursier
 package cli
 
+import java.io.File
 import java.net.{ URL, URLClassLoader }
 
 import caseapp._
@@ -114,6 +115,7 @@ case class Launch(
   val helper = new Helper(
     options.common,
     remainingArgs ++ options.isolated.rawIsolated.map { case (_, dep) => dep },
+    extraJars = options.extraJars.map(new File(_)),
     isolated = options.isolated
   )
 
@@ -123,8 +125,19 @@ case class Launch(
     else
       options.mainClass
 
+  val extraJars = options.extraJars.filter(_.nonEmpty)
+
+  val loader =
+    if (extraJars.isEmpty)
+      helper.loader
+    else
+      new URLClassLoader(
+        extraJars.map(new File(_).toURI.toURL).toArray,
+        helper.loader
+      )
+
   Launch.run(
-    helper.loader,
+    loader,
     mainClass,
     userArgs,
     options.common.verbosityLevel

cli/src/main/scala-2.11/coursier/cli/Options.scala

@@ -188,6 +188,9 @@ case class LaunchOptions(
   @Short("M")
   @Short("main")
     mainClass: String,
+  @Short("J")
+  @Help("Extra JARs to be added to the classpath of the launched application. Directories accepted too.")
+    extraJars: List[String],
   @Recurse
     isolated: IsolatedLoaderOptions,
   @Recurse