BF: Replace inaccurate description of push behavior

[adswa]

As described in #481, the previous description of how push
behaves in datasets with multiple branches was inaccurate,
and resulted from my explorations of push with an explicitly
configured dataset. This change rectifies this, and instead
shows how to configure datasets such that more than just the
current branch is pushed. Fixes #481.

I would appreciate if someone could double check. :)

[mih]

@kyleam This looks good to me. At least for now. It feels as if the exact behavior of push is still subject to changes (in the nearish future).

[kyleam]

@adswa Thanks for adjusting the text.

Sorry I didn't provide feedback even though this has been open for a while. While I do fetch this repo every so often and glance through all the nice additions, I'm not "watching" it, so I didn't get an email about this. With how I intake information from GitHub, that means I didn't know this PR existed :(

[adswa]

Whoops, sorry for not responding for two days already, too, @kyleam! No worries, I should have tagged you if I wanted to ask for explicit feedback. I remember thinking "It's a Saturday, and it concerns a command that isn't even released yet, so why rush/bother others". I promise that if I would appreciate feedback on something I will tag you :)