Fix updating Index Templates V2 (#55556) (#55610)

This change fixes problem with updating Index Templates V2.
Validatation added in #54933 didn't filter list of conflicting templates correctly so
new template was always clashing with itself unless patterns were not changed completely.

server/src/main/java/org/elasticsearch/cluster/metadata/MetadataIndexTemplateService.java

@@ -341,6 +341,7 @@ ClusterState addIndexTemplateV2(final ClusterState currentState, final boolean c
 
         Map<String, List<String>> overlaps = findConflictingV2Templates(currentState, name, template.indexPatterns(), true,
             template.priority());
+        overlaps.remove(name);
         if (overlaps.size() > 0) {
             String error = String.format(Locale.ROOT, "index template [%s] has index patterns %s matching patterns from " +
                     "existing templates [%s] with patterns (%s) that have the same priority [%d], multiple index templates may not " +

server/src/test/java/org/elasticsearch/cluster/metadata/MetadataIndexTemplateServiceTests.java

@@ -358,6 +358,25 @@ public void testAddIndexTemplateV2() throws Exception {
         assertNotNull(state.metadata().templatesV2().get("bar"));
     }
 
+    public void testUpdateIndexTemplateV2() throws Exception {
+        ClusterState state = ClusterState.EMPTY_STATE;
+        final MetadataIndexTemplateService metadataIndexTemplateService = getMetadataIndexTemplateService();
+        IndexTemplateV2 template = IndexTemplateV2Tests.randomInstance();
+        state = metadataIndexTemplateService.addIndexTemplateV2(state, false, "foo", template);
+
+        assertNotNull(state.metadata().templatesV2().get("foo"));
+        assertTemplatesEqual(state.metadata().templatesV2().get("foo"), template);
+
+        List<String> patterns = new ArrayList<>(template.indexPatterns());
+        patterns.add("new-pattern");
+        template = new IndexTemplateV2(patterns, template.template(), template.composedOf(), template.priority(), template.version(),
+            template.metadata());
+        state = metadataIndexTemplateService.addIndexTemplateV2(state, false, "foo", template);
+
+        assertNotNull(state.metadata().templatesV2().get("foo"));
+        assertTemplatesEqual(state.metadata().templatesV2().get("foo"), template);
+    }
+
     public void testRemoveIndexTemplateV2() throws Exception {
         IndexTemplateV2 template = IndexTemplateV2Tests.randomInstance();
         final MetadataIndexTemplateService metadataIndexTemplateService = getMetadataIndexTemplateService();