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But before jumping into the demo I would like

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to give a high level overview of the GIT workflow,

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which will help you better, following the demo. So let

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me start by representing four fundamental elements in the GIT

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workflow which are these four: the workspace which is your

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local directory. The index, also called the stage, and we'll

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see in a minute what the index is. Then, we

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have the local repository. We'll also refer to this as

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HEAD in the, when we explain the different commands

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and then, the word flow. And finally, the remote repository.

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If you consider a file in your work space it

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can be in three possible states. It can be committed

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which means that the data, the latest changes to the

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file are safely stored here. It could be modified, which

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is the case of the file being changed and no,

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none of these changes being saved to the local repository

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so locally modified or it can be staged. And

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stage means that the file is basically part of this

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index. And what that means, that it's been tagged

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to be considered in the next commit. And I know

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that this is not all 100% intuitive, so let's

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look at that again by considering the actual workflow and

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let's see what happens when you issue the different

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commands in git. So the first command that you normally

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run in case you, you're getting access to a remote

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repository, is the git clone command. And the git clone,

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followed by the url for that repository, will create a

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local copy of the repository in your workspace. And of

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course, you don't have to do this step if you're

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creating the repository yourself. The next command that we already

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saw is the command add. And what the command add

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does is to add a file that is in the

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workspace to this index. And we say that after that, the

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file is staged. So it's marked to be committed, but not

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yet committed. And here I'm just mentioning this minus u option.

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If you specify the minus u option, you will also consider deleted

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files File, but let's not get there for now, we'll talk

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about that when we do the demo. As I said, if you

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add the file, it just gets added to this index but

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is not actually committed, so what you need to do, is to

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commit the file, so when you execute git commit, all the

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files that are staged, that are released it here, their changes

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will be committed to the local repository. So your files, as

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I was saying, they can be in three states. They will

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go from the modified state to the stage state when you

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execute the app. And then from the stage state to the

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committed state when you perform a GIT Commit. Okay, so at

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this point your changes are safely stored in the local repository.

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Notice that you can also perform these two steps at

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once by executing a Commit -a. So if you have

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a set of modified files, and all these files are

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already part of the repository, so they're already known to diversion

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control system, you can simply execute a commit -a.

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And what the commit -a command will do, it

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will stage your file and then commit them. All at

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once. So it's a convenient shortcut. Of course, as I said,

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this will not work if the file is a new file.

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So if a file is a new file, you have to manually add

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it. Otherwise commit -a will just stage and commit at once.

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As we discussed when we looked at the diffence between centralized

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and decentralized version console system. We saw that in the case

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of the decentralized, there is a local repository which is this one.

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And then you have to explicitly push your changes to a remote

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repository, and this is exactly what the git push command does. It pushes

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your changes that are in the local repository to the remote repository

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so at this point all of your changes will be

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visible to anyone who has access to the remote repository.

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Now, let's see the opposite flow so how does it

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work when you're actually getting files from the repository instead

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of committing files to the repository. So the first command

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I want to mention is the get fetch command and

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what the get fetch command does is to get files from

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the remote repositories to your local repository, but not yet to

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your working directory. And we will see what is the usefullness of

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doing this operation. Of having the files all in the local respository,

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but not in your local directory. So, what that means, just to

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make sure that we're on the same page. Is that you

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will not see these files when you workspace. You will still have

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your local files here. So this is sort of a physical distinction.

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In order to get your data files from the local repositories to

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your workspace you have to issue another command. Which is

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the command git merge. Git merge will take the changes in

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local repository and get them to your local workspace. So at

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this point your files will be updated. To what is in

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the remote reposity. Or at least what was in the

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remote reposity at the time of the fetch. SImilarly to what

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happened for the add and commit. There's a shortcut which is

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the command git pull. So in case you want to get

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the changes directly. To your work space with a single

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command, you can issue a git pull command and what will

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happen, is that the changes will get collected from the

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remote repository and they will go to your local repository and

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to your work space, at once. So this has the

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same affect as performing a git fetch and a git merge.

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So if we can do everything in one command, why,

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why we want to fetch and berch as two separate operations?

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So one of the reason is because this allows us

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to compare files before we actually get the latest version

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of the files. In particular, I can run the command

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git diff head to get the difference between my local files,

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the files in my working directory, and the files in

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my local repository. So what I can do, I can

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fetch the files from the remote repository, and once I

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fetch these files. I can run a git diff head and

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check what the differences are. And based on the differences decide

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whether I want to merge or not. So while we are talking about

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git diff, there is something else that you can use with the

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diff command. So what you can do, you can run git diff

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without further specifying head. In this case, what the command tell you

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is the difference between the files that you have in your work

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space and the ones that are staged for a commit. So basically,

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what it will be telling you, is that what you could still

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add to the stage for the further commit, and that you

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haven't already. So what local changes will not make it to the

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next commit, basically. And this you can use, for example, as

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a sanity check before doing a commit to make sure all the

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local changes that you have, and that you want to commit,

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are actually staged and therefore will be considered. So now we will

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cover all of the commands that we saw here. In our practical

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demo. But please feel free to refer back to this Git Workflow

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to get a kind of a high level vision. Or maybe you want to keep it next to

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you, because this really gives you the overall structure

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and the overall view of what happens when you

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run the different commands. And it also helps you

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visualize The different elements that are relevant when you're

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using GIT. So the workspace, once more, the index

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or stage, the local repository, and the remote repository.