Common code between verify and blocks
> Following #262
### Tasks
- [ ] common function to gather a range of blocks specifying `from_`, and `to`.
- [ ] common test on this function gathering blocks on a range by chunks
- [ ] two modes for `blocks` explorer:
- current: specify number of blocks from head, 0 default to current window
- [ ] Same as verify: a range of blocks: blocks number `from` an `to`.
- [ ] How to specify/filter the two modes: `--range`, `--from-head`/`--head` (this one would be the default).
This could be a method into a class that would inherit the `@click.command` decorator. Would that work?
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### Later
- [ ] command `blocks` with sub-commands `explorer`, `verify`, …: is this possible with Click?
issue