Feature: generate man pages

[Kixunil]

It'd be really nice to be able to generate man page automatically. The flags library lnd is using already supports generating manpage although a bit awkwardly - by using same code that is used in runtime.

Possible approaches

• Have an additional switch/command in lncli (and ideally also in lnd) that will save the man page in a file/stdout. This is somewhat weird in cross-compiling scenarios.
• Have a very small binary that imports same config code and that binary writes manpage.
• Separate binary as before + automatically run it in release script (never cross compile) and add manpage to the release - I like this the most.

[lightningorb]

I'll take this as it's labelled good first issue.

[lightningorb]

paired with: @mauricepoirrier

man page for lncli generated successfully. Just needs a bit of formatting work else it's pretty much done.

[lightningorb]

Sharing early.

This is in cmd/lncli/main.go:

	docs := GenerateDocs(app);

        f, err := os.Create("program.1")
        if err != nil {
            panic(err)
        }
        defer f.Close()

	f.Write([]byte(docs))

The GenerateDocs function is literally copied from urfave/cli#340 (comment)

Currently we're converting from markdown to man using pandoc, but we're not yet set on the cleanest approach for generating man pages and integrating this with the rest of the codebase neatly. Ongoing.

[Kixunil]

@lightningorb This mentions some ToMan method, maybe you could use it instead?

[mohamedawnallah]

I'm interested in taking on this issue. All seems good to me I've just put the comments in the closed PR where I have some doubts about when implementing this feature. Thanks!