code: function gulpBuildAgentInfo(agentInfoFolder, agentInfoFilename, packageFile) {
      if (agentInfoFilename === undefined) {
          agentInfoFilename = "agent.info.ts";
      }
      if (packageFile === undefined) {
          packageFile = "package.json";
      }
      return () => {
          const gulp = require("gulp");
          const result = generateAgentInfoFile(agentInfoFolder, agentInfoFilename, packageFile);
          return gulp.src(result[0]);
      };
  }
docs: Returns a gulp task function for generating a TypeScript file including agent
  info in the specified folder.
  
  Agent project package information is acquired from the specified package.json
  file and the build mode is determined by environment variable setting
  `COATY_ENV`. Set `COATY_ENV` to "development", "production", "testing", etc.
  before building your application. If the `COATY_ENV` variable is not set, its
  value defaults to "development".
  
  This function is intended to be used in a gulp task definition within a
  gulpfile.
  
  @param agentInfoFolder the folder where to write the agent info file
  @param agentInfoFilename the file name of the agent info file (defaults to
  "agent.info.ts")
  @param packageFile the path to the package.json to extract package
  information from (defaults to "package.json")