I'm more likely to ask what source control you have used. If you say Git, I'm going to ask why. I'm going to figure out if you really understand source code or you just use what's popular. That is not a statement about Git or any other source control. But I don't need to see your github account to figure out what level of developer you are (or what level you think you are).

I use git because I was taught it and have found no reason to transition elsewhere. I know that's not a good reason to use git. If I'm to consider alternatives, I'm going to have to set aside the 10 million other things I could be learning, many of which are actual obstacles to my workflow.

Oh, I could learn SVN. Or Mercurial. Or Node.js, Groovy, MFC, solaris, AngularJS, Adobe Illustrator, Guitar, Unicode, Python, Web Services, Satellite Radio, JNI, C#, Haskell metaprogramming, Android, Client-server models, Nuclear Physics, ASP.net, Flex/Yacc, Cocoa, COM, Blender, DOM, TCP/IP, XML, Finance, Azure, Cassandra, VIM, Emacs, Arch Linux, Regex, Category Theory, Statistics, Maya, Color models, IEEE-754, Compiler optimization, OS design, Database management, LINQ, Piano, Struts, ML, Prolog, Scheme, Homotopy Type Theory, NLTK, GTK+, X windows, WPF, ...

Why would anyone care that I know git and haven't explored other options? Do you happen to need someone who can write source control software?

Well, for starters, the person interviewing you (in this case, ME) DOES know all of the different source control versions. That doesn't mean you have to know them, but it does matter to me why you think yours is best. Mercurial guys think theirs is best. SVN guys think theirs is best. Why? Why not? That tells me a lot more about how you think as a developer than which tool you actually use.

I mean, I had to use ClearCase for years and hated it. But I know how it works and why I hated it.

But I don't think mine is best, I think it is merely good enough.

From this end, it would strike me as a hypocrisy: "I don't care which religion you follow, so long as you believe the one you follow is the best and you can rationalize that to yourself."

That doesn't really tell you much. It's like if you are interviewing a philosopher and say "where is your toga and beard? How you choose your toga and beard style is important to evaluating what kind of philosopher you are." What are you basing that on? Why do you think source control selection is relevant to the work you are trying to do?

It seems to me like a totally pointless question, except for the fact that it is a question and it will fill the time and require someone to talk.

"Because it's popular" is a great way to pick your plumbing, though. The opposite is the awesome developer who is so religious about all the tools and languages that he uses that nobody wants to work with them.

It's a good place to start. But I want to know that the person using a tool has a better understanding of what they are using than "everybody else uses it".

The most popular solution could be the best one. I just want to hire people who think for themselves because I don't have time to do their thinking for them. But first I need to make sure they are really adept at problem solving and can adapt.

I think he was referring to sites that allow you to manage and collaborate with others, etc. e.g., sourceforge

It's a little bit more than that: around 7 years old.