* Rework parameters passing for functions within `ec.rebuild`
This simplifies the overall codebase and allows to cleanly handle parallelization via waitgroups.
* fix copy source
* add tests
* remove tests not useful
* fmt
* nil check
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Co-authored-by: Chris Lu <chrislusf@users.noreply.github.com>
Co-authored-by: chrislu <chris.lu@gmail.com>
