flag: add FlagSet usage examples

[obeyda]

What did you expect to see?

Having some examples on the flag package's docs showing how to create subcommands with FlagSet.

What did you see instead?

There's only a package example and Value interface usage and none of them shows how to use FlagSet to create subcommands.

[mvdan]

The example for https://golang.org/pkg/flag/#Value does use a flagset, but I agree that it's not easy to find. Sending a CL.

[gopherbot]

Change https://golang.org/cl/212757 mentions this issue: flag: add a FlagSet example

[gopherbot]

Change https://golang.org/cl/212599 mentions this issue: flag: add example for flagset

[cagedmantis]

/cc @robpike

[Codinee]

I would like to work on coming up with examples for FlagSet commands usage.

[agnivade]

@Codinee - There is already an active CL for this.

[obeyda]

Any updates you can propose to this CL?

[mvdan]

@obeyda note that I asked for a rebase on the CL so we can re-test and merge.

[mvdan]

Friendly ping @obeyda, as someone else rebased the CL but now there's a missing import due to it. I know it's been some time, but if you can't fix up this patch so we can merge it, we should close the CL so someone else can take this.

[gopherbot]

Change https://go.dev/cl/545736 mentions this issue: flag: Add FlagSet example

[ccmtaylor]

https://go.dev/cl/545736 is marked "ready to submit" in Gerrit. What is the next step?