You have the right idea, you need to get the right select line.
But, unless you really need XSLT -- and for a one-time translation, you really don't -- using any real programming language you're familiar with is going to be faster and easier.
I've done a bit of XSLT stuff, but I've only managed by using the simplest of select lines.
Oh, and when I used XSLT? I needed to preprocess it to get it how I wanted.
@yam655 Yeah, I'm starting to think I should just use the JSON export and some Perl to get it right. Ideally I'd also offer it to other G+ refugees, but perhaps Perl 5 is still OK enough. I mean, having xsltproc installed is basically just as obscure a requirement. 😃
Is the XSLT available in xsltproc still just 1.0? That was one of the reasons for pre/post processing. Some things would be possible with current versions of XSLT, just not with xsltproc.
macOS currently ships with Perl 5.18.2. When major OSes include it out of the box, you probably don't need to fret too much about its use.
@yam655 Hehe, good point. I guess if I use Perl I might as well write a little wep app where people can upload their archives or something like that.