Add retry feature

[birdayz]

Make commands retryable:

...
tasks:
  build:
    retry:
      attempts: 3
      exit_codes:
        - 1
        - 127
    cmds:
     ...

If exit_codes is provided, only the provided exit codes are retryable. otherwise, all exit code are retried.

I have a use case, where a task runs many other tasks via deps. One of them fails, it all fails. In the end, CI retrys the entire task invocation, which will again run all of these parallel tasks. However, it would be much better to only retry the individual task that fails.
I can do the retry within the cmd, but that's not very elegant and re-usable i feel.

[danilobuerger]

Best case, this should also include a delay.

[trulede]

The situation as you describe is resolved by using Task features such as 'sources', 'generates', and 'run'. Subsequent runs of Task will not execute the previously completed tasks. There are additional features 'status', 'preconditions' and 'if' that may also be used.

If you have a particularly flaky command, simply use a shell loop. They are easy to write, concise and capable. But otherwise, use the existing features of Task.