Merge "Report reverse dependencies for dangling rules."

	// Get a list of leaf nodes in the dependency graph from ninja

	executable := config.PrebuiltBuildTool("ninja")

	args := []string{}

	args = append(args, config.NinjaArgs()...)

	args = append(args, "-f", config.CombinedNinjaFile())

	args = append(args, "-t", "targets", "rule")

	common_args := []string{}

	common_args = append(common_args, config.NinjaArgs()...)

	common_args = append(common_args, "-f", config.CombinedNinjaFile())

	args := append(common_args, "-t", "targets", "rule")

	cmd := Command(ctx, config, "ninja", executable, args...)

	stdout, err := cmd.StdoutPipe()

		sb := &strings.Builder{}

		title := "Dependencies in out found with no rule to create them:"

		fmt.Fprintln(sb, title)

		for _, dep := range danglingRulesList {

			fmt.Fprintln(sb, "  ", dep)

		report_lines := 1

		for i, dep := range danglingRulesList {

			if report_lines > 20 {

				fmt.Fprintf(sb, "  ... and %d more\n", len(danglingRulesList)-i)

				break

			}

			// It's helpful to see the reverse dependencies. ninja -t query is the

			// best tool we got for that. Its output starts with the dependency

			// itself.

			query_cmd := Command(ctx, config, "ninja", executable,

				append(common_args, "-t", "query", dep)...)

			query_stdout, err := query_cmd.StdoutPipe()

			if err != nil {

				ctx.Fatal(err)

			}

			query_cmd.StartOrFatal()

			scanner := bufio.NewScanner(query_stdout)

			for scanner.Scan() {

				report_lines++

				fmt.Fprintln(sb, " ", scanner.Text())

			}

			query_cmd.WaitOrFatal()

		}

		ts.FinishAction(status.ActionResult{

			Action: action,

			Error:  fmt.Errorf(title),