Display a warning in the Installed tab if the admin is about to disable or uninstall a detached plugin (#4098)

* Display a warning in the Installed tab if the admin is about to disable or uninstall a detached plugin.

* @since

Co-Authored-By: Oleg Nenashev <o.v.nenashev@gmail.com>

core/src/main/java/hudson/PluginWrapper.java

@@ -84,6 +84,7 @@ import static hudson.PluginWrapper.PluginDisableStatus.ERROR_DISABLING;
 import static hudson.PluginWrapper.PluginDisableStatus.NOT_DISABLED_DEPENDANTS;
 import static hudson.PluginWrapper.PluginDisableStatus.NO_SUCH_PLUGIN;
 import static java.util.logging.Level.WARNING;
+import jenkins.plugins.DetachedPluginsUtil;
 import static org.apache.commons.io.FilenameUtils.getBaseName;
 
 /**
@@ -999,6 +1000,15 @@ public class PluginWrapper implements Comparable<PluginWrapper>, ModelObject {
         return !archive.exists();
     }
 
+    /**
+     * Same as {@link DetachedPluginsUtil#isDetachedPlugin}.
+     * @since TODO
+     */
+    @Exported
+    public boolean isDetached() {
+        return DetachedPluginsUtil.isDetachedPlugin(shortName);
+    }
+
     /**
      * Sort by short name.
      */