Reordering getting started (or introducing sidebar) to help newbie

[tansaku]

I have some feedback from a person new to git that the first time git setup section was a bit confusing:

https://github.com/progit/progit2/blob/master/book/01-introduction/sections/first-time-setup.asc

in that they would have preferred to have the description of the different levels of git config come after the instructions to set up their identity. I think this is partly because they were looking for some specific way to "run git" as specified in the previous section on installation (see #957).

Would it make sense to adjust the ordering here so we see the example config setting first and then have the more detailed explanation after - or moved the detailed explanation to a sidebar?

[ben]

I think the original idea was to give a sense of what the config feature is doing before diving in, but you're right, this is chapter 1. We should be talking to the complete newbie. I'd definitely review a PR that switches things around a bit.

[ben]

I'd prefer that we just move the details to the end. There's probably too much there to fit in a single-page sidebar.