How to use the @ts-common/azure-js-dev-tools.gitDiff function in @ts-common/azure-js-dev-tools

const modifiedFiles: string[] | undefined = statusResult.modifiedFiles;
      if (modifiedFiles) {
        changedFiles.push(...modifiedFiles);
      }
    }

    if (packBaseReference === packHeadReference) {
      if (rawToPack) {
        _logger.logWarn(`The base-reference "${packBaseReference}" is equal to the head-reference "${packHeadReference}". This will result in nothing getting packed because there won't be any changes detected. Please change either the base or head-reference.`);
      } else {
        toPack = PackagesToPack.DifferentVersion;
        _logger.log(`The base-reference "${packBaseReference}" is equal to the head-reference "${packHeadReference}" which means there won't be any changes to pack. Switching "to-pack" to be "${PackagesToPack[toPack]}".`);
      }
    } else {
      const diffResult: GitDiffResult = gitDiff(packBaseReference, packHeadReference, runOptions);
      changedFiles.push(...diffResult.filesChanged);
      if (!changedFiles || changedFiles.length === 0) {
        _logger.logTrace(`Found no changes between "${packBaseReference}" and "${packHeadReference}".`);
      } else {
        _logger.logTrace(`Found the following changed files`)
        for (const changedFilePath of changedFiles) {
          _logger.logTrace(changedFilePath);
        }
      }
    }
  }

  const packageFolderRoot: string = path.resolve(__dirname, "sdk");
  _logger.logTrace(`INFO: Searching for package folders in ${packageFolderRoot}`);
  const packageFolderPaths: string[] | undefined = getPackageFolderPaths(packageFolderRoot);
  if (!packageFolderPaths) {

logger.logInfo(`No head-reference argument specified on command line or in environment variables. Defaulting to "${headReference}".`);

  const modifiedFiles: string[] | undefined = statusResult.modifiedFiles;
  if (modifiedFiles) {
    changedFiles.push(...modifiedFiles);
  }
}

let baseReference: string | undefined = getArgument("base-reference", { environmentVariableName: "baseReference" });
if (!baseReference) {
  baseReference = "master";
  logger.logInfo(`No base-reference argument specified on command line or in environment variables. Defaulting to "${baseReference}".`);
}

if (baseReference !== headReference) {
  const diffResult: GitDiffResult = gitDiff(baseReference, headReference);
  changedFiles.push(...diffResult.filesChanged);
  if (!changedFiles || changedFiles.length === 0) {
    logger.logInfo(`Found no changes between "${baseReference}" and "${headReference}".`);
  } else {
    logger.logVerbose(`Found the following changed files`)
    for (const changedFilePath of changedFiles) {
      logger.logVerbose(changedFilePath);
    }
  }
}

const repositoryFolderPath: string = resolvePath(__dirname, "..");
const packagesFolderPath: string = joinPath(repositoryFolderPath, "sdk");
const packageFolderPaths: string[] | undefined = getPackageFolderPaths(packagesFolderPath);

let exitCode: number = 0;