Add 'is:merge' operator to find changes which are merge commits

This change introduces a new index schema version and reindexing the
changes is required.

Change-Id: If800fce63f6d45419b46e5e624f6872ca3feaba3

Documentation/user-search.txt

@@ -487,6 +487,11 @@ is:wip::
 +
 True if the change is Work In Progress.
 
+[[merge]]
+is:merge::
++
+True if the change is a merge commit.
+
 [[status]]
 status:open, status:pending, status:new::
 +

java/com/google/gerrit/server/index/change/ChangeField.java

@@ -696,6 +696,19 @@ public class ChangeField {
                 return m ? "1" : "0";
               });
 
+  /** Whether the change is a merge commit. */
+  public static final FieldDef<ChangeData, String> MERGE =
+      exact(ChangeQueryBuilder.FIELD_MERGE)
+          .stored()
+          .build(
+              cd -> {
+                Boolean m = cd.isMerge();
+                if (m == null) {
+                  return null;
+                }
+                return m ? "1" : "0";
+              });
+
   /** The number of inserted lines in this change. */
   public static final FieldDef<ChangeData, Integer> ADDED =
       intRange(ChangeQueryBuilder.FIELD_ADDED)

java/com/google/gerrit/server/index/change/ChangeSchemaDefinitions.java

@@ -121,6 +121,7 @@ public class ChangeSchemaDefinitions extends SchemaDefinitions<ChangeData> {
    * Added new fields {@link ChangeField#ATTENTION_SET_USERS} and {@link
    * ChangeField#ATTENTION_SET_FULL}.
    */
+  @Deprecated
   static final Schema<ChangeData> V59 =
       new Schema.Builder<ChangeData>()
           .add(V58)
@@ -128,6 +129,10 @@ public class ChangeSchemaDefinitions extends SchemaDefinitions<ChangeData> {
           .add(ChangeField.ATTENTION_SET_FULL)
           .build();
 
+  /** Added new fields {@link ChangeField#MERGE} */
+  static final Schema<ChangeData> V60 =
+      new Schema.Builder<ChangeData>().add(V59).add(ChangeField.MERGE).build();
+
   /**
    * Name of the change index to be used when contacting index backends or loading configurations.
    */

java/com/google/gerrit/server/query/change/ChangeData.java

@@ -284,6 +284,7 @@ public class ChangeData {
   private Optional<ChangedLines> changedLines;
   private SubmitTypeRecord submitTypeRecord;
   private Boolean mergeable;
+  private Boolean merge;
   private Set<String> hashtags;
   private Map<Account.Id, Ref> editsByUser;
   private Set<Account.Id> reviewedBy;
@@ -953,6 +954,16 @@ public class ChangeData {
     return mergeable;
   }
 
+  @Nullable
+  public Boolean isMerge() {
+    if (merge == null) {
+      if (!loadCommitData()) {
+        return null;
+      }
+    }
+    return parentCount > 1;
+  }
+
   public Set<Account.Id> editsByUser() {
     return editRefs().keySet();
   }

java/com/google/gerrit/server/query/change/ChangeQueryBuilder.java

@@ -597,6 +597,13 @@ public class ChangeQueryBuilder extends QueryBuilder<ChangeData, ChangeQueryBuil
       return new BooleanPredicate(ChangeField.MERGEABLE);
     }
 
+    if ("merge".equalsIgnoreCase(value)) {
+      if (args.getSchema().hasField(ChangeField.MERGE)) {
+        return new BooleanPredicate(ChangeField.MERGE);
+      }
+      throw new QueryParseException("'is:merge' operator is not supported by change index version");
+    }
+
     if ("private".equalsIgnoreCase(value)) {
       if (args.getSchema().hasField(ChangeField.PRIVATE)) {
         return new BooleanPredicate(ChangeField.PRIVATE);

javatests/com/google/gerrit/server/query/change/AbstractQueryChangesTest.java

@@ -2124,6 +2124,29 @@ public abstract class AbstractQueryChangesTest extends GerritServerTests {
     assertQuery("status:open -is:mergeable", change2);
   }
 
+  @Test
+  public void merge() throws Exception {
+    assume().that(getSchema().hasField(ChangeField.MERGE)).isTrue();
+    TestRepository<Repo> repo = createProject("repo");
+    RevCommit commit1 = repo.parseBody(repo.commit().add("file1", "contents1").create());
+    RevCommit commit2 = repo.parseBody(repo.commit().add("file1", "contents2").create());
+    Change change1 = insert(repo, newChangeForCommit(repo, commit1));
+    Change change2 = insert(repo, newChangeForCommit(repo, commit2));
+    RevCommit mergeCommit =
+        repo.branch("master")
+            .commit()
+            .message("Merge commit")
+            .parent(commit1)
+            .parent(commit2)
+            .insertChangeId()
+            .create();
+    Change mergeChange = insert(repo, newChangeForCommit(repo, mergeCommit));
+
+    assertQuery("status:open is:merge", mergeChange);
+    assertQuery("status:open -is:merge", change2, change1);
+    assertQuery("status:open", mergeChange, change2, change1);
+  }
+
   @Test
   public void reviewedBy() throws Exception {
     resetTimeWithClockStep(2, MINUTES);