unresolvedOptionalSelectors.add(selector);
            }
        }

        if (!unresolvedOptionalSelectors.isEmpty()) {
            LOGGER.info("The requested optional projects {} do not exist.", unresolvedOptionalSelectors);
        }

        return resolvedOptionalProjects;
    }

    private List<MavenProject> getChildProjects(MavenProject parent, MavenExecutionRequest request) {

        ExecResult execResult = exec("git show $commit:$filePath")
        if (execResult.returnCode != 0 && execResult.stderr ==~ /path '.*' exists on disk, but not in '.*'/) {
            println("File $filePath does not exist on commit $commit, skip.")
            throw new AbortException()
        }
        return execResult.stdout
    }

    static List<String> branchesOf(String commit) {

  public boolean contains(@CheckForNull Object target) {
    // Necessary for ISS's with comparators inconsistent with equals.
    return indexOf(target) >= 0;
  }

  @GwtIncompatible // super.subListUnchecked does not exist; inherited subList is valid if slow
  /*
   * TODO(cpovirk): if we start to override indexOf/lastIndexOf under GWT, we'll want some way to

	return os.MkdirAll(dirPath, perm)
}

// readDirFn applies the fn() function on each entries at dirPath, doesn't recurse into
// the directory itself, if the dirPath doesn't exist this function doesn't return
// an error.
func readDirFn(dirPath string, filter func(name string, typ os.FileMode) error) error {
	d, err := Open(dirPath)
	if err != nil {
		if osErrToFileErr(err) == errFileNotFound {

        if (entry == null) {
            return null;
        }

        if (graph.isEmpty()) {
            throw new GraphConflictResolutionException("graph with an entry, but not vertices do not exist");
        }

        if (graph.isEmptyEdges()) {
            return null; // no edges - nothing to worry about
        }

        final TreeSet<MetadataGraphVertex> vertices = graph.getVertices();

            StackOverflowError.class,
            e -> e instanceof StackOverflowError);
      }
    };

    // used under GWT, etc., since the override of this method does not exist there
    ImmutableMap<Class<? extends Throwable>, Predicate<Throwable>> exceptions() {
      return ImmutableMap.of();
    }
  }

            StackOverflowError.class,
            e -> e instanceof StackOverflowError);
      }
    };

    // used under GWT, etc., since the override of this method does not exist there
    ImmutableMap<Class<? extends Throwable>, Predicate<Throwable>> exceptions() {
      return ImmutableMap.of();
    }
  }

      if (!GUAVA_PACKAGES.contains(info.getPackageName())) {
        continue;
      }
      if (info.getName().endsWith("GwtSerializationDependencies")) {
        continue; // These classes exist only for the GWT compiler, not to be used.
      }
      if (
      /*
       * At least one of the classes nested inside TypeResolverTest triggers a bug under older JDKs:

        final Path jarPath = ResourceUtil.getPluginPath(artifact.getFileName());
        if (!Files.exists(jarPath)) {
            throw new ThemeException(artifact.getFileName() + " does not exist.");
        }
        return jarPath;
    }

      throw new AssertionError(impossible);
    }
  }

  /**
   * Returns an optional enum constant for the given type, using {@link Enum#valueOf}. If the
   * constant does not exist, {@link Optional#absent} is returned. A common use case is for parsing
   * user input or falling back to a default enum constant. For example, {@code
   * Enums.getIfPresent(Country.class, countryInput).or(Country.DEFAULT);}
   *