getManifestRequestCode(appID, depotID, manifestID, branchName, branchPassword, callback) {
		if (typeof branchPassword == 'function') {
			callback = branchPassword;
			branchPassword = null;
		}

		return StdLib.Promises.timeoutCallbackPromise(10000, null, callback, (resolve, reject) => {
			this._sendUnified('ContentServerDirectory.GetManifestRequestCode#1', {
				app_id: appID,
				depot_id: depotID,
				manifest_id: manifestID,
				app_branch: branchName,
				branch_password_hash: branchPassword ? StdLib.Hashing.sha1(branchPassword) : undefined
			}, (body, hdr) => {
				let err = Helpers.eresultError(hdr.proto);
				if (err) {
					return reject(err);
				}

				resolve({requestCode: body.manifest_request_code});
			});
		});
	}
Gets a manifest request code
@param {int} appID
@param {int} depotID
@param {string} manifestID
@param {string} branchName
@param {string} [branchPassword]
@param {function} [callback]