Genesis options flag for init

[rigelrozanski]

provide a flag --module-options on init to interface with the InitState function which satisfies the Middleware interface. (https://github.com/cosmos/cosmos-sdk/blob/develop/modules/coin/handler.go#L84)

Currently the only way to change genesis options is through manually baked in app options in the genesis file (https://github.com/cosmos/cosmos-sdk/blob/develop/cmd/basecoin/commands/init.go#L117). By adding a flag which has the capability to to initialize a genesis middleware param we eliminate the need for many apps to require their own init.go file with custom genesis creation.

Open to suggestions as to the best format for multiple options to be passed in, so far I was thinking something that might look like:

basecoin init --module-options=<name1>/<optionkey>/<value>,<name2>/<optionkey>/<value>

[ethanfrey]

I like it.

Some comments:

How about --option as the flag name. The other is very long?

Can we just use the option flag multiple times?

[ethanfrey]

Typically the value will be json and have commas inside making parsing your format difficult.

With the change in the flag itself, I agree with the behavior change.

And maybe we can rename plugin_options in the genesis file as well... But that is probably a different issue

[rigelrozanski]

okay --option is good if you don't think it's to ambiguous... Didn't realize we could reuse a flag multiple times... great, this solves the second problem of using comma because of JSON.

[ethanfrey]

I could swear I saw this working with cobra, using: https://godoc.org/github.com/spf13/pflag#StringSlice

But I can't find a proper reference, but someone else did this with stdlib: https://lawlessguy.wordpress.com/2013/07/23/filling-a-slice-using-command-line-flags-in-go-golang/

And some interesting flag handling options here:
https://github.com/spf13/pflag

note also the aliasing and deprecation issues, to help with migrations, and that pesky long_name vs long-name issue

[ethanfrey]

Here is the proof it can be called multiple times: https://github.com/spf13/pflag/blob/master/string_slice.go#L42-L54

[ebuchman]

relevant #324

[rigelrozanski]

resolved in init refactor