Handle relative path configuration file

Author: bagage

Diff for: src/main/java/io/gitlab/arturbosch/detekt/config/DetektConfigurationForm.form

@@ -30,7 +30,7 @@
             </constraints>
             <properties>
               <text value=""/>
-              <toolTipText value="Path to detekt configuration file"/>
+              <toolTipText value="Path to detekt configuration file. A relative path can be used, and will be relative to project directory."/>
             </properties>
           </component>
         </children>

Diff for: src/main/kotlin/io/gitlab/arturbosch/detekt/config/DetektConfigStorage.kt

@@ -7,6 +7,7 @@ import com.intellij.openapi.components.Storage
 import com.intellij.openapi.components.StoragePathMacros
 import com.intellij.openapi.project.Project
 import com.intellij.util.xmlb.annotations.Tag
+import java.io.File
 
 /**
  * @author Dmytro Primshyts
@@ -15,7 +16,7 @@ import com.intellij.util.xmlb.annotations.Tag
     name = "DetektProjectConfiguration",
     storages = [(Storage(StoragePathMacros.WORKSPACE_FILE))]
 )
-class DetektConfigStorage : PersistentStateComponent<DetektConfigStorage> {
+class DetektConfigStorage(val project: Project) : PersistentStateComponent<DetektConfigStorage> {
 
     @Tag
     var enableDetekt: Boolean = false
@@ -34,6 +35,12 @@ class DetektConfigStorage : PersistentStateComponent<DetektConfigStorage> {
 
     @Tag
     var rulesPath: String = ""
+        set(value) {
+            field = if (value.isBlank() || File(value).isAbsolute)
+                value
+            else
+                project.basePath + "/" + value
+        }
 
     override fun getState(): DetektConfigStorage? = this