add default for gas-price and gas-limit (#1699)

[deaswang]

Fixes #1699

[frrist]

Looks good to me (these are the default values from the wiki), thanks!

[deaswang]

already rebase master. @travisperson @frrist

[deaswang]

strange, sometime pass, sometime fail at different test case here. how to retest.

[anorth]

The values have changed since this was reviewed. Please see my comment here: #1896 (comment)

[travisperson]

We removed the ability for zero priced gas. (Issue #2523; PR #2605)

https://github.com/filecoin-project/go-filecoin/blob/3dbbf3a515ab9c9c48bb37da5dafc7bce77e17c0/consensus/validation.go#L67-L69

I'm not sure how these tests are passing unless the code above is dead. My guess is that we are specifying all gas prices already actually everywhere.

[anorth]

In that case I don't think we should have a default gas price baked into the code. Until we have something more sophisticated, I think we should require users to specify a gas price, and thus a bound on their cost. cc @mishmosh for comment.

Sorry for the misdirection from #1699, @deaswang. Can we fix up the help documentation to match behaviour instead?

[deaswang]

OK. Wait for final decide. if gas price is required, it should move to Arguments. Options donot support require option.
https://godoc.org/github.com/ipfs/go-ipfs-cmdkit

[anorth]

In that case I think maybe we should just not fix this, and wait for #3098 and a CLI implemented on top of it to solve all our problems.

[frrist]

Sorry for the misdirection on this @deaswang, we are going to close this and reevaluate after #3098 lands.