A new property called task can be used to assign a name. If it is
specified, then the task's actions must be nested under an actions
property, and an if property can be used to make it conditional.
Just like on a link action, the value is executed in the shell. If
it has a non-zero exit code (failure), the whole task is skipped.
This allows tasks to group actions that only apply in certain
conditions (e.g. on certain OSes or in certain configurations),
and allows all actions (not just link) to be conditional.
If there is no task property, then the task behaves exactly as
it did previously.
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