The update check

Once a day turnout looks up its own latest release and, if you are behind, says so at the end of a command:

turnout 0.10.2 is available (you have 0.10.1).
  Update with `turnout self-update`

That is the whole feature. It never interrupts, never prompts, and never changes what a command does. Acting on it is turnout self-update.

It does not slow anything down

The lookup does not happen while you wait. A command that finds the cached answer stale spawns a detached background process and exits immediately; that process does the network call and writes the result to update-check.json in the data directory.

The consequence is worth stating plainly: the notice you see describes what the previous run found. A brand-new installation says nothing on its first command, and tells you about an update on the next one. That is the price of never adding latency to a command you actually asked for.

When it stays quiet

• More often than once a day. The cached answer is reused; only a stale cache triggers a lookup.
• Output is piped. The notice goes to stderr and only when that is a terminal, so it never lands in the middle of something a script is parsing.
• Nothing is newer. Versions are compared numerically, so 0.10.0 correctly beats 0.9.0, and a final release beats its own release candidate.
• The lookup failed. No network, no DNS, a proxy in the way - the attempt is recorded and retried tomorrow, not on every command. Nothing is printed and no command fails because of it.

Turning it off

Set TURNOUT_UPDATE_CHECK to 0, false, no or off:

export TURNOUT_UPDATE_CHECK=0

Nothing is then looked up, cached or printed. The check also switches itself off when CI is set, where the notice has no reader and every run starts from a clean machine.

Where the version comes from

The tag is read from the Location header of the /releases/latest redirect on github.com - not from api.github.com, whose unauthenticated calls are capped at 60 per hour per IP address. Behind a shared address that cap is reached by other people, and a check that fails for everyone at once is worse than no check. A redirect that does not end in a version tag is ignored rather than reported as a release.

Nothing is sent along with the request beyond a turnout/<version> user agent: no identifiers, no telemetry, no record of which apps or servers you have.