Add script dependencies modification tracker, some optimizations

compiler/frontend/src/org/jetbrains/kotlin/script/KotlinScriptDefinition.kt

@@ -23,6 +23,7 @@ import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.parsing.KotlinParserDefinition
 import org.jetbrains.kotlin.psi.KtScript
 import java.io.File
+import kotlin.comparisons.compareValues
 import kotlin.reflect.KClass
 import kotlin.script.templates.standard.ScriptTemplateWithArgs
 
@@ -42,13 +43,33 @@ open class KotlinScriptDefinition(val template: KClass<out Any>) {
     open fun <TF> getDependenciesFor(file: TF, project: Project, previousDependencies: KotlinScriptExternalDependencies?): KotlinScriptExternalDependencies? = null
 }
 
-interface KotlinScriptExternalDependencies {
+interface KotlinScriptExternalDependencies : Comparable<KotlinScriptExternalDependencies> {
     val javaHome: String? get() = null
     val classpath: Iterable<File> get() = emptyList()
     val imports: Iterable<String> get() = emptyList()
     val sources: Iterable<File> get() = emptyList()
     val scripts: Iterable<File> get() = emptyList()
+
+    override fun compareTo(other: KotlinScriptExternalDependencies): Int =
+            compareValues(javaHome, other.javaHome)
+            .chainCompare { compareIterables(classpath, other.classpath) }
+            .chainCompare { compareIterables(imports, other.imports) }
+            .chainCompare { compareIterables(sources, other.sources) }
+            .chainCompare { compareIterables(scripts, other.scripts) }
 }
 
 object StandardScriptDefinition : KotlinScriptDefinition(ScriptTemplateWithArgs::class)
 
+private fun<T: Comparable<T>> compareIterables(a: Iterable<T>, b: Iterable<T>): Int {
+    val ia = a.iterator()
+    val ib = b.iterator()
+    while (true) {
+        if (ia.hasNext() && !ib.hasNext()) return 1
+        if (!ia.hasNext() && !ib.hasNext()) return 0
+        if (!ia.hasNext()) return -1
+        val compRes = compareValues(ia.next(), ib.next())
+        if (compRes != 0) return compRes
+    }
+}
+
+private inline fun Int.chainCompare(compFn: () -> Int ): Int = if (this != 0) this else compFn()