pseudo-merge.c: do not generate empty pseudo-merge commits

The previous commit demonstrated it is possible to generate empty
pseudo-merge commits, which is not useful as such pseudo-merges carry no
information.

Ensure that we only generate non-empty groups by not pushing a new
commit onto the bitmap_writer when that commit has no parents.

Signed-off-by: Taylor Blau <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: ttaylorr

pseudo-merge.c

@@ -357,8 +357,10 @@ static void select_pseudo_merges_1(struct bitmap_writer *writer,
 			p = commit_list_append(c, p);
 		} while (j % group->stable_size);
 
-		bitmap_writer_push_commit(writer, merge, 1);
-		writer->pseudo_merges_nr++;
+		if (merge->parents) {
+			bitmap_writer_push_commit(writer, merge, 1);
+			writer->pseudo_merges_nr++;
+		}
 	}
 
 	/* make up to group->max_merges pseudo merges for unstable commits */
@@ -398,8 +400,9 @@ static void select_pseudo_merges_1(struct bitmap_writer *writer,
 			p = commit_list_append(c, p);
 		}
 
-		bitmap_writer_push_commit(writer, merge, 1);
-		writer->pseudo_merges_nr++;
+		if (merge->parents) {
+			bitmap_writer_push_commit(writer, merge, 1);
+			writer->pseudo_merges_nr++; }
 		if (end >= matches->unstable_nr)
 			break;
 	}

t/t5333-pseudo-merge-bitmaps.sh

@@ -390,7 +390,7 @@ test_expect_success 'pseudo-merge reuse' '
 	)
 '
 
-test_expect_failure 'empty pseudo-merge group' '
+test_expect_success 'empty pseudo-merge group' '
 	git init pseudo-merge-empty-group &&
 	(
 		cd pseudo-merge-empty-group &&