fsck: use ERROR_MULTI_PACK_INDEX

The multi-pack-index was added to the data verified by git-fsck in
ea5ae6c "fsck: verify multi-pack-index". This implementation was
based on the implementation for verifying the commit-graph, and a
copy-paste error kept the ERROR_COMMIT_GRAPH flag as the bit set
when an error appears in the multi-pack-index.

Add a new flag, ERROR_MULTI_PACK_INDEX, and use that instead.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>

Author: derrickstolee

builtin/fsck.c

@@ -49,6 +49,7 @@ static int name_objects;
 #define ERROR_PACK 04
 #define ERROR_REFS 010
 #define ERROR_COMMIT_GRAPH 020
+#define ERROR_MULTI_PACK_INDEX 040
 
 static const char *describe_object(struct object *obj)
 {
@@ -906,7 +907,7 @@ int cmd_fsck(int argc, const char **argv, const char *prefix)
 			midx_argv[2] = "--object-dir";
 			midx_argv[3] = odb->path;
 			if (run_command(&midx_verify))
-				errors_found |= ERROR_COMMIT_GRAPH;
+				errors_found |= ERROR_MULTI_PACK_INDEX;
 		}
 	}