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Now in the last lesson we spoke about some of the more basic variants of version control.
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Now in this lesson I want to talk about branches and branching.
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Now let's start off with a simple example say if we had version 1 and 2,
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so two commits that were made to our local repository.
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Now at this point we realize that we want to maybe try out something different, maybe build a new feature
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or just to mess around with a new idea or concept.
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So what we can do is instead of continuing to commit to the master branch which is the main branch that
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you see here, we can also create a side branch. So we can create as many branches as we like.
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So after the second commit, we create a new branch and we start committing to this new branch or this
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experimental branch. We add some features and we write some code.
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Now simultaneously we can continue working on the main branch putting out all those essential updates
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or bits of code that are maintaining our main project but at the same time we can continue to update
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and work on this experimental branch trying things out and committing our experiments to this experimental
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branch.
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So now we have two branches that are parallel to each other and they can be developed simultaneously.
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Now if at some point in the future that we decide that that experiment was really fruitful and the feature
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that we built in it was really really great and we'd like to merge it back to the main branch or to
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the main project, then that can be done really easily as well by simply placing a merge request in.
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And we can bring all of those changes that we experimented with, that we messed around with back to the
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main project and check to see if there's any conflicts with the main branch code.
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And if not or if after a little bit of editing then we can bring all of those changes into the main
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working master branch. And then we can continue working from here on to the next commit or we can make
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more branches. And very often what you see in practice is that there'll be multiple branches being worked
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on at the same time for any given large project.
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And the reason is because sometimes you are developing new features, sometimes you are fixing bugs and
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all of these things may break your main project so you don't want to do it on the master branch.
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You only want to put it onto the master branch once you've tested, once you know that everything is working
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fine and then you can bring your code back to the working copy ready for shipment and deployment.
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So let's take a look at how this would work in reality.
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Now let's say we navigate back to our story directory
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and inside here we've still got our previous three chapters and they are under version control.
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So if we just have a look at git log you can see that this is currently the most recent commit and it's
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also mirrored in our remote.
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So let's try and do this locally first.
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If I decided I want to create a new branch you can simply just git branch and specify the name of your
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new branch.
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So I'm going to add a space related plot to my story.
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So let's call our branch alien-plot, hit enter. And now you can check out what branches you have by just
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writing git branch without the name. And you can see that you've got one brand called alien-plot and
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another one called master and the * shows you which branch you are currently on.
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So we're currently on the master branch.
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We can switch to the alien-plot by simply writing git checkout alien-plot.
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Okay.
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So as it says we have now switched to the branch called alien-plot.
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Now it is inside this branch that I'm going to make some changes to my chapters.
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So let's try doing that.
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Now I'm going to make some completely nonsensical hum modification to my files.
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So let's change chapter 1, let's change chapter 2.
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Okay, here we go.
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Okay.
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So we've made some modifications to
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chapter 1 and chapter 2 and we've decided to change some of the preexisting written text to integrate a
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space themed or alien themed plot.
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So let's go ahead and commit that.
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So remember we have to do git add and then git commit -m.
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And our message is going to be 'modify chapter 1 and 2 to have alien theme'.
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OK now hit enter and we've made our commits.
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So now if we do a git log, we can see that we have two commits made on the master branch and we have
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one commit made on the alien-plot branch.
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So now let's say that we go back on to our master branch.
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So whenever you're confused where you are, you can always do a git branch to check and see where the
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* is and the * is obviously where you are.
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So let's do a git checkout master to go back to the master branch. So you can see that our master branch
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is unchanged with respect to the space or alien-plot that we did just now.
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Nothing has changed over here.
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So while on the master branch I'm going to create a new file, I'm going to call it chapter4.txt.
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And inside chapter 4
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let's let's add something.
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Okay and hit enter and save.
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By the way I have no idea what I'm typing.
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I'm now making up and destroying, probably in the process, a masterpiece.
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But it's OK.
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So we now have a chapter 4 on our master branch and I'm going to go ahead and do a git add and git
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commit.
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Now there's ways of combining add and commit together in the same command.
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But I think if you need to git, it's always good to really know in your head exactly what's going on.
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So I recommend actually separating those two bits out.
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So let's go ahead and give it a commit message, add chapter r.
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OK.
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So git log.
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Let's see what have we got.
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So we are currently only looking at the master branch and we have three commits.
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This is the position of our remote,
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so on our GitHub repository this was the latest commit that it could see.
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But on a local get repository this is in fact the latest commit, the one that we just made where we added
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chapter 4.
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And you can see that if I switch between the branches say if I go over to alien-plot branch and hit
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enter, you can see the local files actually changed as I switch branches.
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So let's just say that I'm quite happy with the changes I've made in terms of my alien-plot addition
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and I would like to merge these changes back into my master branch.
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So I've done a little bit of experimentation on a separate branch,
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I've messed with a few things,
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and I think it was a great experiment
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so I'm going to put it back into our main master branch.
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So in order to do that what you have to do is go back to the master branch, so git checkout master,
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and while we're on the master branch we're going to merge the changes inside the alien-plot branch.
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So we use the command git merge and we're going to specify the branch name which was alien-plot.
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Hit enter and this opens up Vim which is a text editor and this allows you to add a merge message if
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you wish.
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And alternatively as we're going to do here, we're just going to leave it empty and you to write.
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"
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q! to save and quit. And you can see now I've actually absorbed those changes from the
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alien-plot.
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So I'm on my master branch and you can see that because if I do git branch, I am on the master branch.
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So the alien-plot branch still exists by the way.
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So on the master branch if you have a look at git log you can see that I've got some of the previous
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commits but I've also got this merge branch alien-plot which was my most recent commit.
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So now at this point let's do a git push to our origin master and remember to add the -u flag.
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So that's completed.
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And let's check it out online.
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So if we go over to our story repository, you can see that there's now five commits.
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So we modify chapter 1 and 2, we added chapter 4 and we merge the alien-plot branch.
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So if you go into insights, graphs and go to network,
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now if I can zoom in on this network graph and get rid of the tag, then you can see this is the process
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that we've gone through.
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So this is the master branch where we did chapter 1 and chapter 2. And then at this point after
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I created chapter 2 and 3, I created a new branch.
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And while inside this branch I made a commit that modified chapter 1 and 2 to have an alien theme.
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And then on the master branch I continued developing the master brand adding a chapter 4.
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But subsequently I realized that I did a great job on adding alien themes to our storyline and I decided
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to merge it back into the main branch.
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So this is basically a graphical representation of what's been going on. Now you can do everything I
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just did inside GitHub itself and it's actually really easy to do.
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So let's go ahead and create a brand new repository and I'm going to call this one story2 because
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that's how imaginative I am, clearly not suited for story writing.
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Now it's really important
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we're going to leave our repository as public but you're going to check this box to initialize your repository
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with a readme.
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Now a readme is simply a text file that tells other people what your Git
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Hub repository is all about.
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So if you go on to any repository, lets just search for something like--
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And we go over here,
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you can see that this part that comes below the list of files is the readme. And some people format
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this really heavily so that you can show various flags but you can also tell people how to use your
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library, how to incorporate it into their project,
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basically a whole bunch of useful stuff for
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anybody who is looking at your repository.
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So now we've got our new repository so you can click on the readme file and you can make some edits
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if you wish.
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But what we're going to do is we're going to go into our main story 2 repository and I'm just going
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to create a new file.
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So this is going to be again chapter1.txt and in my new file I'm just going to say, 'This is a story'.
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I think I'm pretty much given up on writing stories now. And we're going to make a commit
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so this is going to be create 
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chapter 1. And we're going to commit directly to the master branch.
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So commit new file.
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Ok so now that we've got chapter 1 and we are on the branch master, at this point I'm going to create
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a new branch and let's call this new branch experimental.
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Okay, so now we have experimental and it takes you straight to the experimental branch copying over everything
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that you had at that point inside the master branch.
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And now inside this experimental branch, I'm going to make an edit to my chapter 1. So I'm going to click
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on the file not over here but over here, and I'm going to click on the pencil button to edit this file.
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This is a story. This-- Nothing like a bit of confidence in your story writing to make it better
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right?
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Okay. So now let's commit these changes and let's say 'Update chapter 1 to be more upbeat'.
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Okay. Now we're going to commit and we're committing, so always check to see where you're committing to
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because sometimes when you have a lot of branches and you're switching branches then it can get quite
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confusing.
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So we're committing to the experimental branch and we're going to go ahead and commit those changes.
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Now let's switch back to our master branch and you can see immediately this is reflected. So that new
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line that we had previously is now gone.
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So let's go back to our main repository file.
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You can see that you've already got this little notification here which is telling you that you've got
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a experimental branch and you can compare between your master and experimental and make a pull request.
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So we're going to talk about pull requests in more detail later on.
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But basically this is telling you, 'Hey you've got changes that are not reflected in your master branch. Do
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you want to pull those changes over to your master branch?'
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So right now that's not we're going to do.
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But instead on our master branch, so check to make sure that master is checked, we're going to create a
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new file and we're going to call it chapter2.txt. And we're going to say, 'This is an even better
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chapter.' Okay.
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So let's say, 'Create chapter 2' and we're committing to the master branch.
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So commit that file and then we're going to check out what the structure of our repository looks like
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now inside graphs and inside network. So you can see that we've got a initial commit and then we have
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our created chapter 1 and then after chapter 1 we decide to make a branch that was experimental and
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then we continued where we left off in the master branch.
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So now what I want to do is I want to go into that master branch and I want to merge those changes in
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the experimental branch over.
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So I want to pull those changes from the experimental branch to the master branch.
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So, in order to pull you have to be in the place that you're going to do the pulling which is the master
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branch.
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And while we're here I'm going to say New pull request and this takes me to the compare page.
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So here I can say that my base is my master branch and I want to compare it with my experimental branch.
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So we can see that the difference is only this line, so plus this line. When it's red, it's an erasure and
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when it's a plus it's an addition.
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So whereas inside my master branch, this is all I've got inside chapter 1. In my experimental branch
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I've got all of this.
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So I have to say that I prefer this version in the experimental branch.
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So I'm very happy with what I did in the experiment
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so I'm going to create a pull request that is going to merge these two branches.
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So now once I've done that I'm going to merge those two branches.
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So I'm going to say merge experimental branch to master and go ahead and confirm the merge.
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Now you can see it's almost more straightforward doing it on the terminal, but you get used to the interface
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and this is not so complex either.
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So now if we have a look at our network graph,
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you can see that the experimental branch was pulled back to the master branch and merged.
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So that was us creating a branch and merging it.
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Now why don't you go ahead and have a go and create your own repository both locally and as well as
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on GitHub
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and you know write a story or write a poem anything, you like and check out the amazingness that is
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branching using Git.