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Before getting to the demo, I want to say a few

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more things. In particular, I discuss the main don'ts in VCS. So,

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what are some things that you don't want to do, and

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you should not do, when you're using a version control system? And

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I'm going to mention two, in particular, because these are two

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that I witnessed several times when I was teaching this class and

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also when collaborating with other people. So, there are two kinds

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of resources that you don't want to add to a VCS normally.

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One is derived files. For example an executable that is

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derived by compiling a set of source files, where the

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source files all already in the repository. At that point,

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there is no reason to also add the executable file in

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the repository. So in general, any executable file should not

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be added to repository. The second class of files that I

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want to mention is these bulky binary files. If you

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have one such file, it is normally not a good idea

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to store them under a version control system, to store them

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in the repository. There might be exceptions to these rules, but in

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general, these are the kind of files that you want to

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keep local, and you don't want to put in the VCS repository.

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Another typical mistake, and that happens all the time, especially to

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novice users of VCS. Is that you get your file from VCS

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and so you get your local copy of the file that

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was in the VCS, and you want to make some changes, and

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before making the changes you decided, no, no let me actually save

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a local copy of the file, and I'm going to work on

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that one. Or let me save it before I modify it, or

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let take a snap shot of a whole tree of files. Just because

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I don't really trust the fact that VCS is going to be

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able to help and is going to be able to recover from possible

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mistakes. Never ever do that. I have seen that done many times,

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and it always leads to disasters. First of all it is useless, and

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second it's risky. Because then what happens is that at

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the time in which you have to turn in your assignment,

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in the case you are doing an assignment, but even in

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more serious situation, when you have to turn in your code,

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for example to your colleagues. You always end up being confused

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about which is the version that you're really using. So absolutely

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no local copies. No local redundancy when you're using a version

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control system. Trust the version control system, and trust the version

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control system to be able to manage your versions. You

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can always save it, commit it, retrieve previous versions, and you'll

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be able to do everything that you can do by copying

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the file yourself, and even more. So again, try the VCS.