Respect empty previous-build changelog and avoid backfilling older repo history

src/main/java/io/papermc/fill/gradle/task/PublishToFillTask.java

@@ -212,6 +212,10 @@ private List<Commit> gatherCommits(Git git, FillExtension extension) {
 
       final List<BuildResponse> builds = this.fetchPreviousBuilds(extension);
       if (!builds.isEmpty()) {
+        if (hasLatestBuildWithEmptyCommits(builds)) {
+          return commits;
+        }
+
         // not every build might have commits, we have to find the last one that did have some
         BuildResponse lastBuildWithCommits = null;
         for (final BuildResponse build : builds) {
@@ -242,6 +246,11 @@ private List<Commit> gatherCommits(Git git, FillExtension extension) {
     return commits;
   }
 
+  @VisibleForTesting
+  static boolean hasLatestBuildWithEmptyCommits(final List<BuildResponse> builds) {
+    return !builds.isEmpty() && builds.getFirst().commits().isEmpty();
+  }
+
   private boolean tryMarkPreviousBuildCommit(final Git git, final RevWalk revWalk, final RevCommit currentCommit, final Commit lastCommit) throws IOException {
     final ObjectId lastBuildObjectId = git.getRepository().resolve(lastCommit.sha());
     if (lastBuildObjectId == null) {

src/test/java/io/papermc/fill/gradle/task/PublishToFillTaskTests.java

@@ -0,0 +1,50 @@
+/*
+ * Copyright 2024 PaperMC
+ *
+ * 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
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * 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 io.papermc.fill.gradle.task;
+
+import io.papermc.fill.model.BuildChannel;
+import io.papermc.fill.model.response.v3.BuildResponse;
+import java.time.Instant;
+import java.util.List;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class PublishToFillTaskTests {
+  @Test
+  void latestBuildWithEmptyCommitsReturnsTrue() {
+    final BuildResponse latest = new BuildResponse(2, Instant.EPOCH, BuildChannel.STABLE, List.of(), Map.of());
+    final BuildResponse older = new BuildResponse(1, Instant.EPOCH, BuildChannel.STABLE, List.of(), Map.of());
+
+    assertTrue(PublishToFillTask.hasLatestBuildWithEmptyCommits(List.of(latest, older)));
+  }
+
+  @Test
+  void latestBuildWithCommitsReturnsFalse() {
+    final BuildResponse latest = new BuildResponse(2, Instant.EPOCH, BuildChannel.STABLE, List.of(
+      new io.papermc.fill.model.Commit("abc", Instant.EPOCH, "msg")
+    ), Map.of());
+
+    assertFalse(PublishToFillTask.hasLatestBuildWithEmptyCommits(List.of(latest)));
+  }
+
+  @Test
+  void emptyBuildListReturnsFalse() {
+    assertFalse(PublishToFillTask.hasLatestBuildWithEmptyCommits(List.of()));
+  }
+}