Add TTL to taskfile.Cache

[jlucktay]

Description

This PR implements part of the remote Taskfiles experiment (#1317) that is currently ongoing.

Implementation notes

• taskfile.Cache has a new private time.Duration field for the TTL setting.

  • The default TTL setting for the cache is 24 hours. Should this be shorter/longer? 4 hours? 1 week?

• The taskfile package has some new exports:

  • the default TTL value described above, in a const.
  • a static error: ErrExpired.
  • a CacheOption type, and a WithTTL func returning this type, to help with creation of new Cache structs.

• The main task executable has a new flag (currently gated by the TASK_X_REMOTE_TASKFILES experiment) to override the default cache TTL setting, outlined below.

Flow diagram

There is a flowchart sketched out here on this branch to describe the overall flow.

New CLI behaviour

$ TASK_X_REMOTE_TASKFILES=1 task --help 
…
Options:
…
      --remote-cache-ttl duration   TTL of remote Taskfiles downloaded into the local cache. (default 24h0m0s)

Resolves #1402.

[jlucktay]

Thank you for the notes @ccoVeille 🙂 🙏
I'll give things a once-over soon.

[ccoVeille]

While you are simply applying a gofumpt on this.

I'm surprised to see:

• the error is ignored
• this variable name is in uppercase
• the variable is apparently used only in one test.

I would expect this variable to be used only where needed and to check the possible error

[vmaerten]

Hi !
Thanks for working on this 🔥 To me 24h is too short.
I'll take my example but it can work for other.

We include only taskfiles we own in our company, so I know when I need to fetch a new version. I am always running with offline mode to avoid unecessary http call (and it's faster to not fetch X differents remote taskfiles).

I think we could add an env variable to control the cache duration (this way we do not need to worry about passing the flag each time we download a remote file)

One more thing, the chart does not reflect the real behavior.

As we said, the "offline" first will be done in another PR, you need to update the chart

@pd93 any thought on this?

[vmaerten]

It should go in the errors package.
You need to be a bit more specific in the error message, for example write wich file is expired