[HUDI-80] Leverage Commit metadata to figure out partitions to be cleaned for Cleaning by commits mode (#1008)

hudi-common/src/main/java/org/apache/hudi/common/HoodieCleanStat.java

@@ -115,7 +115,7 @@ public class HoodieCleanStat implements Serializable {
 
     public Builder withEarliestCommitRetained(Option<HoodieInstant> earliestCommitToRetain) {
       this.earliestCommitToRetain =
-          (earliestCommitToRetain.isPresent()) ? earliestCommitToRetain.get().getTimestamp() : "-1";
+          (earliestCommitToRetain.isPresent()) ? earliestCommitToRetain.get().getTimestamp() : "";
       return this;
     }
 
@@ -124,4 +124,16 @@ public class HoodieCleanStat implements Serializable {
           earliestCommitToRetain);
     }
   }
+
+  @Override
+  public String toString() {
+    return "HoodieCleanStat{"
+        + "policy=" + policy
+        + ", partitionPath='" + partitionPath + '\''
+        + ", deletePathPatterns=" + deletePathPatterns
+        + ", successDeleteFiles=" + successDeleteFiles
+        + ", failedDeleteFiles=" + failedDeleteFiles
+        + ", earliestCommitToRetain='" + earliestCommitToRetain + '\''
+        + '}';
+  }
 }

hudi-common/src/main/java/org/apache/hudi/common/table/timeline/HoodieActiveTimeline.java

@@ -139,7 +139,7 @@ public class HoodieActiveTimeline extends HoodieDefaultTimeline {
   /**
    * Get only pure commits (inflight and completed) in the active timeline
    */
-  public HoodieTimeline getCommitTimeline() {
+  public HoodieTimeline   getCommitTimeline() {
     return getTimelineOfActions(Sets.newHashSet(COMMIT_ACTION));
   }