Command line flag to open localhost:1313

[rjc123]

As a not-very-technical hugo user
I would like to generate my site locally to test (heavily using hugo server -D) and see it immediately upon build in a local browser.
So that I can review it works as I would have expected.

hugo server -D && open http://localhost:1313 doesn't function, as it requires the server command to complete before opening the browser
open http://localhost:1313 && hugo server -D does function as needed, but doesn't match the order one would think about these things.

The best result would be hugo server -D -o -- so that the browser opens to the localhost immediately on the first build of the site, leaving the server running.

[bep]

I think we have had this discussion before, and I think the argument against it was that it wasn't a good/simple multi platform way to do this. But I see now that this exists, which looks solid enough:

https://github.com/pkg/browser

As to flags, I would suggest we go for -O (uppercase). I have tried to make it lowercase=configuration, uppercase=actions. Some of the uppercase are a little bit borderline, but I think it makes sense.

So:

hugo server -O

[sevein]

Related issues:

• open browser when run on mac #5595
• [Feature Request] hugo server should open in browser after successfully started #6293
• Open Browser after the server has started #7410