code: async function getFile(repoId, repository, filePath, branchName) {
    logger.trace(`getFile(filePath=${filePath}, branchName=${branchName})`);
    const azureApiGit = await azureApi.gitApi();
    const item = await azureApiGit.getItemText(
      repoId,
      filePath,
      null,
      null,
      0, // because we look for 1 file
      false,
      false,
      true,
      {
        versionType: 0, // branch
        versionOptions: 0,
        version: getBranchNameWithoutRefsheadsPrefix(branchName),
      }
    );
  
    if (item && item.readable) {
      const fileContent = await streamToString(item);
      try {
        const jTmp = JSON.parse(fileContent);
        if (jTmp.typeKey === 'GitItemNotFoundException') {
          // file not found
          return null;
        }
        if (jTmp.typeKey === 'GitUnresolvableToCommitException') {
          // branch not found
          return null;
        }
      } catch (error) {
        // it 's not a JSON, so I send the content directly with the line under
      }
      return fileContent;
    }
    return null; // no file found
  }
docs: if no branchName, look globaly
  @param {string} repoId
  @param {string} repository
  @param {string} filePath
  @param {string} branchName