subcommand --help doesn't show global options

[tersec]

Even when they're required to usefully use the subcommand, e.g.,:

$ build/ncli_db bench --help
Usage: 

ncli_db bench [OPTIONS]...

The following options are available:

 --slots            Number of slots to run benchmark for.
 --storeBlocks      Store each read block back into a separate database.
 --printTimes       Print csv of block processing time.
 --resetCache       Process each block with a fresh cache.

But to use this subcommand, one has to also specify --db:

$ build/ncli_db  --help | head
Usage: 

ncli_db [OPTIONS]... command

The following options are available:

 --db           Directory where `nbc.sqlite` is stored.
 --network      The Eth2 network preset to use.

Available sub-commands:

So build/ncli_db bench --help does not document sufficiently how to use ncli_db bench.

[unixpi]

@zah came across this problem today. is it easy to fix?

[jangko]

we have compile time tree path selector to detect duplicate name and abbr. maybe we should display the help message using similar algorithm. The help text should be displayed in a heirarchical order if subcommand help requested.

see #32