Add wrapper function for go-sockaddr templating

[thevilledev]

This PR bundles the many templating functionalities offered by hashicorp/go-sockaddr to consul-template. These template functionalities are especially useful in cases where consul-template is run upon system startup, for example by cloud-init, to render interface IP addresses to configuration files.

Also adds vendoring for go-sockaddr, which might make this PR look like a bit daunting (1,1M additions).

Documentation updated as well.

[pearkes]

I think there may be a mistake in the vendoring here -- I don't think all of these are dependencies required by go-sockaddr. Can you review how you did the vendoring and double check you're only pulling in the necessary deps?

[pearkes]

Thanks for the contribution!

[thevilledev]

Thanks @pearkes for the heads up. I just did dep ensure -add github.com/hashicorp/go-sockaddr/template while doing this and it appears to add a bunch of other non-related dependencies as well. If you clone consul-template and just run dep ensure you'll see that it fetches a bunch of stuff that it thinks are missing from vendoring. Is this expected?

Anyway, I fixed the vendoring in this PR to just include github.com/hashicorp/go-sockaddr. Only other package it depends on is github.com/hashicorp/errwrap but it's already included in the project vendoring.

Let me know if there's anything else we need to do before merging.

[aaglenn]

will this get merged before the next release? I have an admittedly odd use case, specifically...but I would really, really enjoy having this in consul-template.

[eikenb]

Hey @vtorhonen, since you submitted your pull request we've implemented a policy of requiring a signed CLA before merging. Would you please consider signing the CLA? Thanks.

[hashicorp-cla]

All committers have signed the CLA.

[thevilledev]

@eikenb CLA signed and branch rebased. Sorry for the wait. :)

[eikenb]

@vtorhonen No problem. Thanks for doing that.

I'm making one more bug sweep right now, but after I plan on reviewing all outstanding PRs to see what I can merge. I'll get to this then (think a couple weeks).

Thanks.

[eikenb]

Hey @vtorhonen, reviewing all the PRs now and would like to ask if you could add a simple test in funcs_test.go for this. It won't be a blocker as this is such a simple function, but I've been asking all the other new functions for one and really would like to have better coverage of the functions directly (vs. going through the template rendering).

Thanks.