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>> And I thought that the best way to break the ice on version

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control systems and Git and some other

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related concepts was to interview John Britton who

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works with GitHub. So let's go and see what John has to say about

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Git, about version control systems in general,

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and about GitHub. John is in Tapei, if I'm not wrong.

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>> That's correct.

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>> Okay so we're, you know we couldn't

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go there so we're interviewing him remotely. And I

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want, I just want to thank you so much and John for agreeing to talk to us.

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>> Thank you very much for having me it was my pleasure.

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>> And, I'm just going to ask, a few

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general questions because John is an expert on,

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Git and GitHub. John is a developer and

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a community builder is active in both the

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open source and the open education areas. And

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as an educational liaison we have, is working

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to improve Computer Science education by bringing the

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principles of open source into the classroom. And

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I'm going to start with an general question,

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which is what is a version control system?

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>> So, a version control system is

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a tool that software developers use. Anybody

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who's doing you know, working with digital

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assets, digital projects can also use for

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keeping track of, you know, revisions of your project, and when I say revisions, I

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mean essentially snapshots of your project over time. So you can imagine doing

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some work and then every so often, be it, every couple of

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hours, every couple of days, saving a permanent snapshot of your project.

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>> Why is this useful? I understand that

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it is nice to take a snapshot of your

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project, but what did you do with the

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snapshot afterwards? I think the most immediately obvious benefit

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to having snapshots of your project to keeping

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revisions is that you can go back. If you

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have ever worked on a project and got to

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a point where you solved a bunch of your

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problems, and there is just one more step to do. And

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you start working on trying to solve that last step, and

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you break things, you make it worse then it was an

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hour ago. At that point its easier to just go back

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to what you had then trying to figure out what you

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broke. So you can always go back in time, and the

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other big one is being able to collaborate with multiple people,

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so its pretty seldom these days that you. Work on a production

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totally on your own. It's most common to work in, you

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know, in teams and small groups. And so, using a revision

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control system allows you to collaborate with other people. And make

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sure that you don't step on each other's toes as you're working.

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>> Alright, that's great, because those are exactly some of the

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topics that we're going to cover in the lesson. And so since we're

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going to talk about the specifics of version control system which is

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Git and you're definitely an expert in, in Git. So what would

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you say is specifically special about Git? What characterizes it

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and how does it compare to other version control systems.

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>> So if any of you have used version control systems before, you

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may have heard of something like subversion, CVS, or maybe a commercial solution

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like ProForce. I think the main important characteristics of Git are first that

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it's open source. And the second,

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that it's a distributed version control system.

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So what that means, the distributed version

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control system is essentially a system for tracking

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revisions of your software that doesn't have any

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central repository. So the biggest characteristic is that

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I can do my work and you can also work on the same project at

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the same time without communicating with each other

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and without communicating to a central system.

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>> Okay, great. And so now that we saw what Git is, what is

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GitHub and how does it fit into

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this picture of the distributed, revision control system?

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>> So GitHub is, the world's largest code host, and we essentially have a

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website where you can collaborate with people

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when you're writing code. There's two ways you

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can use GitHub. You can use it publicly for open source and you can use

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it in private within your team, or your company, or within your class. And, Git

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Hub started out just as a way to host your Git repositories. But it's

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actually grown into quite a bit more. It's

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an entire collaboration system around your code.

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>> How many users do you have?

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>> I would say that we're approaching five million.

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I don't know the exact number. We're definitely more

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than four million right now. But yeah, I'd say

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somewhere, somewhere close to between four and five million.

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>> So that's a lot space I'd guess. Terabytes of disk

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space, I would imagine.

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>> There are a lot of GIT repositories on, on our servers.

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>> Something else you want to say? I

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guess that the when taking about GitHub there's one

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thing that you kind of can't leave out and

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that's that's a feature that's called a pull request.

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So when you're using GitHub, you can share

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your Git repository, do some work, and actually do

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do a code review. Of proposed changes which

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is what we call a pull request on github.com.

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Essentially what it lets you do is have a discussion

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about a set of proposed changes and leave feedback in

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line with the code. You could say for example, this

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method needs to be re-factored or I think I found if

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off by one error here, just different kinds of feedback

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so that before you totally integrate some proposed changes. You have,

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kind of a conversation about what your code. And I

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think that's really valuable when you are working in a team.

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>> Thank you, John, that was very informative and

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thanks again for taking the time to talk to us.

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>> No problem, thanks for having me. I'll talk to you soon.

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>> Let's thank again John for enlightening us

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on some aspects of version control systems, Git and

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GitHub. And now, let's go over some of the

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topics that we discussed with John to recap them.