Backward compatibility of airborn server and airborn update with airborn

core.js defines a variable core_version, which is a positive integer indicating requirements/expectations that the version has of airborn-server.

If it's absolutely necessary, you can send specific core_versions messages (e.g., along the lines of, please upgrade). To see how, check out getServerMessages in core.js.

However, please keep in mind that, during upgrading, the following requirements remain true. In other words, if you break them, the normal upgrade process breaks, and users have to use /repair instead. At least tell them so.

• 3: The latest version.
  • Doesn't support deleting or moving files in an upgrade.
• 2: (Exists only on airborn-dev.)
  • Doesn't support transactions. Thus, upgrading Airborn is unsafe.
  • [airborn-update] Requires /current and /currentId instead of /v2/*. /current should be a zip with a folder airborn which contains the contents of /Core
• undefined: The first versions of core.js didn't have a core_version defined. (Exists only on airborn-dev.)
  • Requires the global variable S3Prefix.
  • You also can't send those versions messages.