fix for #293: as per https://docs.oracle.com/javase/8/docs/api/java/nio/file/Path.html#subpath-int-int- subpath shall return a relative path (#394)

Author: stefanofornari

src/main/java/software/amazon/nio/spi/s3/S3Path.java

@@ -257,10 +257,6 @@ public S3Path subpath(int beginIndex, int endIndex) {
         }
 
         var path = String.join(PATH_SEPARATOR, pathRepresentation.elements().subList(beginIndex, endIndex));
-        if (this.isAbsolute() && beginIndex == 0) {
-            path = PATH_SEPARATOR + path;
-        }
-
         if (endIndex == size && !pathRepresentation.hasTrailingSeparator()) {
             return from(path);
         } else {

src/test/java/software/amazon/nio/spi/s3/S3PathTest.java

@@ -336,6 +336,8 @@ public void relativize() {
         var bcd = fileSystem.getPath("b/c/d/");
         var bcdObject = fileSystem.getPath("b/c/d/object");
 
+        assertFalse(root.relativize(ab).isAbsolute());
+
         assertEquals(fileSystem.getPath(""), absoluteObject.relativize(absoluteObject));
         assertEquals(fileSystem.getPath("../.."), abcd.relativize(ab));
         assertEquals(fileSystem.getPath("e/"), abcd.relativize(abcde));