refactor: move code to new structure

[mrossinek]

Summary

This is the follow-up to #722

Details and comments

This PR uses the approach describes in https://stackoverflow.com/a/44036771 to "copy" files while preserving the blame history in both locations.

⚠️ This PR must be merged withOUT squashing all commits (I may however still be able to clean up some of the commits (e.g. the CI changes and main merges)

Closes #701 #702 #703 #704 #705 #706 #707 #708 #709 #710 #711

[mrossinek]

The history preserving aspect of this PR is now working as can be seen under the following two links:

• https://github.com/Qiskit/qiskit-nature/blame/refactor/qiskit_nature/second_q/algorithms/excited_states_solvers/__init__.py
• https://github.com/Qiskit/qiskit-nature/blame/refactor/qiskit_nature/algorithms/excited_states_solvers/__init__.py

[mrossinek]

I also marked this PR to be closing all of the code relocation issues. I will open separate issues for the planned refactorings within the modules in the near future 👍

[ElePT]

Yay! Git blame works for both the old and the new modules!

[coveralls]

Pull Request Test Coverage Report for Build 2691663016

• 7854 of 9396 (83.59%) changed or added relevant lines in 150 files are covered.
• 7 unchanged lines in 6 files lost coverage.
• Overall coverage decreased (-0.5%) to 84.199%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
qiskit_nature/list_or_dict.py	17	18	94.44%
qiskit_nature/second_q/algorithms/excited_states_solvers/eigensolver_factories/eigensolver_factory.py	7	8	87.5%
qiskit_nature/second_q/algorithms/excited_states_solvers/excited_states_solver.py	15	16	93.75%
qiskit_nature/second_q/circuit/library/ansatzes/puccd.py	39	40	97.5%
qiskit_nature/second_q/circuit/library/ansatzes/succd.py	42	43	97.67%
qiskit_nature/second_q/circuit/library/initial_states/hartree_fock.py	37	38	97.37%
qiskit_nature/second_q/circuit/library/initial_states/vscf.py	31	32	96.88%
qiskit_nature/second_q/drivers/base_driver.py	6	7	85.71%
qiskit_nature/second_q/drivers/electronic_structure_driver.py	15	16	93.75%
qiskit_nature/second_q/drivers/gaussiand/gaussian_log_result.py	169	170	99.41%

Files with Coverage Reduction	New Missed Lines	%
qiskit_nature/properties/second_quantization/electronic/angular_momentum.py	1	88.57%
qiskit_nature/properties/second_quantization/electronic/dipole_moment.py	1	91.79%
qiskit_nature/properties/second_quantization/electronic/integrals/integral_property.py	1	90.36%
qiskit_nature/properties/second_quantization/electronic/magnetization.py	1	86.27%
qiskit_nature/properties/second_quantization/electronic/particle_number.py	1	91.23%
qiskit_nature/algorithms/excited_states_solvers/qeom.py	2	82.61%

Totals
Change from base Build 2677814739:	-0.5%
Covered Lines:	17760
Relevant Lines:	21093

---

💛 - Coveralls

[ElePT]

One small comment, the tutorials I removed (5,6 and 9) are still removed in this PR. It doesn't make sense to migrate them, but shouldn't we keep the old version of these together with the old version of the repo until we fully deprecate it? I also took a quick look at the docs and they seem ok to my untrained eye.

[mrossinek]

One small comment, the tutorials I removed (5,6 and 9) are still removed in this PR. It doesn't make sense to migrate them, but shouldn't we keep the old version of these together with the old version of the repo until we fully deprecate it?

Hm that's a good point actually. For the docs I decided (based on a discussion with @manoelmarques and previous input from @woodsp-ibm) that only the new code is documented in the API (i.e. the old code no longer has API documentation). Nonetheless, I agree that it makes sense to keep the legacy tutorials in place. I will re-add those in an upcoming commit 👍

I also took a quick look at the docs and they seem ok to my untrained eye.

Thanks 👍

[mrossinek]

For reviewing purposes it might be easiest, if you do a commit-by-commit review. The 4 commits do the following:

1. merges Migrate modules to new location #722 (the relocation of the old code into the new structure, updating all imports, etc.)
2. "only" moves all of the old code to some "dummy" locations and upgrades the copyright in the process.
3. merges the previous two commits into one another (because these were parallel and not linear, since they moved the same files into separate locations). This merge commit changed 8 __init__ files mostly related to copyright.
4. "reverts" the second commit, moving the old code back from the "dummy" locations into its original place. In doing so, some minor updates are included to ensure the CI works

[mrossinek]

After an offline discussion, we decided to remove the tutorials for the code that is also no longer part of the public API docs. The code in question is still being unittested and the tutorials still exist on stable where they are being run, too 👍