docs: explaining the plugins at the root README.md

Adjusting the test for root environment

Change-Id: I6c4229113995992054441bceab6374f0c49b23b5

README.md

@@ -1,13 +1,20 @@
-![experimental](https://img.shields.io/badge/stability-experimental-red.svg)
+This repository hosts the Google App Engine Maven and Gradle plugins.
+
+User documents:
+
+- [App Engine Maven Plugin](https://cloud.google.com/appengine/docs/standard/java-gen2/using-maven)
+- [App Engine Gradle Plugin](https://cloud.google.com/appengine/docs/standard/java-gen2/using-gradle)
 
 # Google App Engine Plugins Core Library
 
+![experimental](https://img.shields.io/badge/stability-experimental-red.svg)
+
 IMPORTANT:
 This library is used by Google internal plugin development teams to share App Engine
 related code. Its use for any other purpose is highly discouraged and unsupported.
 Visit our [App Engine documentation](https://cloud.google.com/appengine/docs/admin-api/)
 for more information on Google supported clients for App Engine administration.
- 
+
 # Requirements
 
 This library requires Java 1.8 or higher to run.

appengine-plugins-core/src/test/java/com/google/cloud/tools/io/FilePermissionsTest.java

@@ -96,7 +96,10 @@ public void testSubDirectoryCannotBeCreatedDueToPreexistingFile() throws IOExcep
  public void testDirectoryCannotBeCreatedDueToUnwritableParent() throws IOException {
  Path dir = Files.createDirectory(Paths.get(parent.toString(), "child"));
  Assume.assumeTrue(dir.toFile().setWritable(false)); // On windows this isn't true
+ // In Linux, the root user can create a file in a non-writable directory
+ Assume.assumeFalse("root".equals(System.getProperty("user.name")));
  dir.toFile().setWritable(false);
+
  try {
  FilePermissions.verifyDirectoryCreatable(Paths.get(dir.toString(), "bar"));
  Assert.fail("Can create directory in non-writable parent");