Mark certain types @Incubating in preparation for 2.0.0 GA

rewrite-core/src/main/java/org/openrewrite/ChangePublisher.java

@@ -19,6 +19,7 @@
 
 import static java.util.stream.Collectors.toList;
 
+@Incubating(since = "2.0.0")
 public interface ChangePublisher {
     void publish(Collection<Change<?>> changes);
 

rewrite-core/src/main/java/org/openrewrite/Generate.java

@@ -22,6 +22,7 @@
  * for example, format (if some of the refactoring visitors are responsible for formatting) the new generated
  * source in a manner that best suits the project being operated on.
  */
+@Incubating(since = "2.0.0")
 public interface Generate<S extends SourceFile> {
     Collection<S> generate();
 }

rewrite-core/src/main/java/org/openrewrite/Incubating.java

@@ -0,0 +1,29 @@
+/*
+ * Copyright 2020 the original author or authors.
+ * <p>
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * https://www.apache.org/licenses/LICENSE-2.0
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.openrewrite;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Target;
+
+/**
+ * This is a feature that is experimental and may yield a breaking change in a minor release.
+ */
+@Documented
+@Target({ElementType.METHOD, ElementType.TYPE, ElementType.CONSTRUCTOR})
+public @interface Incubating {
+    String since();
+}

rewrite-core/src/main/java/org/openrewrite/Metadata.java

@@ -15,5 +15,6 @@
  */
 package org.openrewrite;
 
+@Incubating(since = "2.0.0")
 public interface Metadata {
 }

rewrite-core/src/main/java/org/openrewrite/Validated.java

@@ -28,6 +28,7 @@
 
 import static java.util.stream.StreamSupport.stream;
 
+@Incubating(since = "2.0.0")
 public interface Validated extends Iterable<Validated> {
     boolean isValid();
 

rewrite-core/src/main/java/org/openrewrite/ValidationException.java

@@ -21,6 +21,7 @@
  * Turns a set of {@link Validated.Invalid} into a throwable exception, which is used to throw an unchecked exception
  * at runtime when one or more properties are invalid.
  */
+@Incubating(since = "2.0.0")
 public class ValidationException extends IllegalStateException {
     private final Validated validation;
 

rewrite-core/src/main/java/org/openrewrite/git/GitChangePublisher.java

@@ -22,6 +22,7 @@
 import org.eclipse.jgit.transport.UsernamePasswordCredentialsProvider;
 import org.openrewrite.Change;
 import org.openrewrite.ChangePublisher;
+import org.openrewrite.Incubating;
 import org.openrewrite.Metadata;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -30,6 +31,7 @@
 import java.util.Collection;
 import java.util.Map;
 
+@Incubating(since = "2.0.0")
 @RequiredArgsConstructor
 public class GitChangePublisher implements ChangePublisher {
     private static final Logger logger = LoggerFactory.getLogger(GitChangePublisher.class);

rewrite-core/src/main/java/org/openrewrite/git/GitMetadata.java

@@ -15,8 +15,10 @@
  */
 package org.openrewrite.git;
 
+import org.openrewrite.Incubating;
 import org.openrewrite.Metadata;
 
+@Incubating(since = "2.0.0")
 public enum GitMetadata implements Metadata {
     HEAD_COMMIT_ID,
     HEAD_TREE_ID,

rewrite-core/src/main/java/org/openrewrite/git/GithubChangePublisher.java

@@ -22,6 +22,7 @@
 import org.kohsuke.github.GitHub;
 import org.openrewrite.Change;
 import org.openrewrite.ChangePublisher;
+import org.openrewrite.Incubating;
 import org.openrewrite.Metadata;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
@@ -38,6 +39,7 @@
  * This publisher is best suited for changes to a single file per repository. Otherwise, multiple commits
  * are generated, one for each changed file.
  */
+@Incubating(since = "2.0.0")
 public class GithubChangePublisher implements ChangePublisher {
     private static final Logger logger = LoggerFactory.getLogger(GithubChangePublisher.class);
 

rewrite-core/src/main/java/org/openrewrite/git/GithubMetadata.java

@@ -15,8 +15,10 @@
  */
 package org.openrewrite.git;
 
+import org.openrewrite.Incubating;
 import org.openrewrite.Metadata;
 
+@Incubating(since = "2.0.0")
 public enum GithubMetadata implements Metadata {
     REPOSITORY,
     ORGANIZATION

rewrite-core/src/main/java/org/openrewrite/refactor/FindIndent.java

@@ -15,6 +15,7 @@
  */
 package org.openrewrite.refactor;
 
+import org.openrewrite.Incubating;
 import org.openrewrite.SourceVisitor;
 import org.openrewrite.Tree;
 import org.openrewrite.internal.StringUtils;
@@ -32,6 +33,7 @@
 /**
  * Discover the most common indentation level of a tree, and whether this indentation is built with spaces or tabs.
  */
+@Incubating(since = "2.0.0")
 public class FindIndent extends SourceVisitor<Void> {
     private final SortedMap<Integer, Long> indentFrequencies = new TreeMap<>();
     private final int enclosingIndent;