automatic gas estimation

[ncitron]

Description

Adds automatic gas estimation to seth mktx if ETH_GAS is not set. Since seth mktx is the underlying for seth send and dapp create, dapptools users will likely never have to input gas limits manually.

Checklist

• tested locally
• added automated tests
• updated the docs
• updated the changelog

[MrChico]

Very nice, been wanting this for some time. I have fixed ci on master, could you rebase so we can run it again?

[ncitron]

This should be good to go now. I've made a couple of changes so that instead of directly calling eth_estimateGas, I make all gas estimations through seth estimate (which I made a slight modification to).

I also made sure to do this gas estimation in both seth send and seth mktx. This is because if you use an RPC signer, just adding the estimation in seth mktx is not sufficient.

[d-xo]

This is a very nice UX upgrade, thanks a lot! We definitely need tests before merging, (you can add tests to this file).

I'm a little worried that there may be some error (either in seth, or the node doing the estimating) that may result in us automatically setting a very high gas value. I think we should at least display the value that we get back from seth estimate and potentially also ask for user confirmation if we're running in an interactive terminal?

[d-xo]

can we put this in an else for the above if statement?

[d-xo]

Why only for --create?

[ncitron]

If SETH_CREATE is unset, then we are doing a normal transaction that has a recipient. If not, we are creating a contract, and TO must be unset since this is a requirement for a contract creation tx.