Adjust BWC version on mapping version

The introduction of mapping version on index metadata has been
backported to 6.x. This commit adjusts the BWC version around mapping
version to account for this backport.

Author: jasontedor

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

@@ -684,7 +684,7 @@ private static class IndexMetaDataDiff implements Diff<IndexMetaData> {
             index = in.readString();
             routingNumShards = in.readInt();
             version = in.readLong();
-            if (in.getVersion().onOrAfter(Version.V_7_0_0_alpha1)) {
+            if (in.getVersion().onOrAfter(Version.V_6_5_0)) {
                 mappingVersion = in.readVLong();
             } else {
                 mappingVersion = 1;
@@ -724,7 +724,7 @@ public void writeTo(StreamOutput out) throws IOException {
             out.writeString(index);
             out.writeInt(routingNumShards);
             out.writeLong(version);
-            if (out.getVersion().onOrAfter(Version.V_7_0_0_alpha1)) {
+            if (out.getVersion().onOrAfter(Version.V_6_5_0)) {
                 out.writeVLong(mappingVersion);
             }
             out.writeByte(state.id);
@@ -760,7 +760,7 @@ public IndexMetaData apply(IndexMetaData part) {
     public static IndexMetaData readFrom(StreamInput in) throws IOException {
         Builder builder = new Builder(in.readString());
         builder.version(in.readLong());
-        if (in.getVersion().onOrAfter(Version.V_7_0_0_alpha1)) {
+        if (in.getVersion().onOrAfter(Version.V_6_5_0)) {
             builder.mappingVersion(in.readVLong());
         } else {
             builder.mappingVersion(1);
@@ -804,7 +804,7 @@ public static IndexMetaData readFrom(StreamInput in) throws IOException {
     public void writeTo(StreamOutput out) throws IOException {
         out.writeString(index.getName()); // uuid will come as part of settings
         out.writeLong(version);
-        if (out.getVersion().onOrAfter(Version.V_7_0_0_alpha1)) {
+        if (out.getVersion().onOrAfter(Version.V_6_5_0)) {
             out.writeVLong(mappingVersion);
         }
         out.writeInt(routingNumShards);
@@ -1370,8 +1370,8 @@ public static IndexMetaData fromXContent(XContentParser parser) throws IOExcepti
                     throw new IllegalArgumentException("Unexpected token " + token);
                 }
             }
-            if (Assertions.ENABLED && Version.indexCreated(builder.settings).onOrAfter(Version.V_7_0_0_alpha1)) {
-                assert mappingVersion : "mapping version should be present for indices created on or after 7.0.0";
+            if (Assertions.ENABLED && Version.indexCreated(builder.settings).onOrAfter(Version.V_6_5_0)) {
+                assert mappingVersion : "mapping version should be present for indices created on or after 6.5.0";
             }
             return builder.build();
         }

server/src/main/java/org/elasticsearch/index/mapper/MapperService.java

@@ -249,7 +249,7 @@ private void assertMappingVersion(
             final Map<String, DocumentMapper> updatedEntries) {
         if (Assertions.ENABLED
                 && currentIndexMetaData != null
-                && currentIndexMetaData.getCreationVersion().onOrAfter(Version.V_7_0_0_alpha1)) {
+                && currentIndexMetaData.getCreationVersion().onOrAfter(Version.V_6_5_0)) {
             if (currentIndexMetaData.getMappingVersion() == newIndexMetaData.getMappingVersion()) {
                 // if the mapping version is unchanged, then there should not be any updates and all mappings should be the same
                 assert updatedEntries.isEmpty() : updatedEntries;