Implement method for JobCalculation to create a restart builder

[sphuber]

Fixes #230

The get_builder method will return a "clean" builder for the given
JobProcess, without any inputs defined. Here we implement get_builder_restart
for the JobCalculation that will also return a JobProcessBuilder but with
the inputs and options pre-set with those that were used for the original node.
The builder can then immediately be resubmitted to run another instance of that
calculation, while of course giving the chance to change one or more inputs.

For example:

calculation = load_node(<pk>)  # Some completed JobCalculation node
builder = calculation.get_builder_restart()
results = run(builder)

[codecov-io]

Codecov Report

Merging #1962 into develop will decrease coverage by 0.07%.
The diff coverage is 14.28%.

@@             Coverage Diff             @@
##           develop    #1962      +/-   ##
===========================================
- Coverage    67.56%   67.49%   -0.08%     
===========================================
  Files          324      324              
  Lines        33342    33390      +48     
===========================================
+ Hits         22529    22538       +9     
- Misses       10813    10852      +39

Impacted Files	Coverage Δ
aiida/work/process_builder.py	87.69% <0%> (ø)	⬆️
...implementation/general/calculation/job/__init__.py	41.95% <14.58%> (-1.71%)	⬇️
...orm/implementation/general/calculation/__init__.py	80.6% <0%> (+0.86%)	⬆️

---

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[ltalirz]

Do we need a new method for this or can/should this be handled by passing a parameter of get_builder ?
Also, should we review now or should we wait until it is unblocked?

[sphuber]

I could not implement this with a toggle keyword in get_builder because that one is a class method, and this needs to be an instance method, since you are restarting from a specific JobCalculation instance. Regarding it being blocked: it simply depends on the other PR #1961 , but once that is merged, this implementation should be sufficient, so we can already go through the review process here.

[giovannipizzi]

Can we add a test for this new function? (+ the two comments)

[giovannipizzi]

Does this work? This does builder.options = {...}, can this be done directly or should we loop?

[sphuber]

I tested this manually and it works, because builder.options is just a mapping namespace, so assigning a dictionary works. But I will write some unit tests

[giovannipizzi]

I'm not sure link.replace(namespace, '') is safe, e.g. if the sub-namespace has the same name it would remove both. Better link[len(namespace):] or something equivalent

[sphuber]

Good point

[sphuber]

This is fixed

[coveralls]

Pull Request Test Coverage Report for Build 3839

• 12 of 17 (70.59%) changed or added relevant lines in 1 file are covered.
• 6 unchanged lines in 4 files lost coverage.
• Overall coverage increased (+7.2%) to 67.878%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
aiida/orm/implementation/general/calculation/job/init.py	12	17	70.59%

Files with Coverage Reduction	New Missed Lines	%
aiida/common/hashing.py	1	91.09%
aiida/orm/implementation/sqlalchemy/group.py	1	88.27%
aiida/orm/implementation/general/calculation/init.py	2	80.6%
aiida/control/postgres.py	2	93.67%

Totals
Change from base Build 3838:	7.2%
Covered Lines:	24124
Relevant Lines:	35540

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💛 - Coveralls

[sphuber]

@giovannipizzi I addressed your comments and added some unit tests, so it's ready for a second review