Going deeper on fork orchestration

[tiagofilipe12]

This PR intends to at the very least increase the level of forkception, i.e., the ability to had forks inside forks.
For now it just handles one fork inside another fork, but has no capacity to handle a third fork. Also and importantly, fork can proceed a fork, i.e. we can have something like this:

const pipeline3 = join(
  task0,
  fork(
      fork(
        task1,
        task3
      ),
      task6
  ),
  task5
)

[codecov-io]

Codecov Report

Merging #72 into dev will decrease coverage by 0.04%.
The diff coverage is 87.87%.

@@            Coverage Diff             @@
##              dev      #72      +/-   ##
==========================================
- Coverage   81.88%   81.83%   -0.05%     
==========================================
  Files          37       37              
  Lines         861      881      +20     
  Branches      102      107       +5     
==========================================
+ Hits          705      721      +16     
- Misses        156      160       +4

Impacted Files	Coverage Δ
lib/orchestrators/fork.js	100% <ø> (ø)	⬆️
lib/lifecycle/resolve-input.js	73.33% <ø> (-0.44%)	⬇️
lib/task.js	100% <ø> (ø)	⬆️
lib/orchestrators/join.js	92.3% <87.87%> (-4.19%)	⬇️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 7359ced...db98270. Read the comment docs.

[thejmazz]

is the number of nested forks supported "hardcoded" based on these nested if/else blocks?

[tiagofilipe12]

This PR now also includes new pipelines for testing multiple inputs as well as new uid generation strategy in which upstream tasks are included in uid creation. Check this GSoC17 entry.

[tiagofilipe12]

Ok, I think it is ready to merge now, but codecov complains about code that is necessary for some of the tests I ran. Maybe you ( @thejmazz ) can find a way to simplify the code.

[tiagofilipe12]

Also added a concurrency pipeline example using bluebird Promise.

[thejmazz]

As long as tests are passing I don't mind merging even if code coverage drops. However, if you look at the coverage, it is just that if (forkee.info.props) and else if (forkee.info.type === 'fork') are not being ran in any of the tests. So if you can take a look how to resolve that, it will probably be enough to satisfy codecov.