Friday Session 2. Github and Source Control Workflow.srt

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[MUSIC]                         

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Stanford University.            
>> Welcome everyone to          

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our Friday section of CS193P.   
I'm Junjie, one of your TAs.    

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And today, I'm gonna            
talk about the GitHub and       

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the source control              
workflow in Xcode 9. So,        

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what is source control?         
Like have you used like         

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some source control             
systems like GitHub?            

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Yeah, so as a software          
developer, you will like,       

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almost like it's                
a necessary skill set for       

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you to learn how to use         
source control systems.         

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Like big companies like         
Facebook and Google,            

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they all have their own         
source control systems. And     

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it's very important for you to  
master those skills before you  

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really go into the industry.    
So what is source control?      

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Why should we matter?           
Why should we care about it?    

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It allows you to track your     
code changes over time.         

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You can revert your files       
back to a previous state.       

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You can compare different       
versions of code side by side.  

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And it also makes               
it a lot easier for             

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you to work with                
other teammates. And            

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like when bugs happen, it's     
much easier to take it down.    

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Today, our topic is one of the  
biggest source control system   

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in the world, and               
it's built right into Xcode 9.  

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Xcode 9 has done a lot of       
great things to integrate       

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GitHub to make it               
very easy to use. So            

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I'm gonna try to demo you some  
of the basics in Xcode 9,       

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how to use GitHub. Before       
that, you should register       

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an account in github.com.       
The repository,                 

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the public repository or        
a repo, is free. And, a repo    

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is just like a code directory   
for you to store the code.      

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And if you register using       
your Stanford email account,    

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you can get the private         
repository for free. I highly,  

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highly encourage you to use     
a private repo to manage        

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all your assignments,           
all your cost projects.         

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And it's much easier for        
you to collaborate with your    

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teammates, and in-              
>> Remind people not to make    

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it public, though.              
>> Yeah, yeah.                  

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>> [CROSSTALK] the public       

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to private.                     
>> So                           

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that's why you wanna register   
using your Stanford email.      

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You would never like up,        
upload                          

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your assignments onto GitHub    
using a public repository cuz   

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like you don't know who will    
just download all the code and  

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copy, copy out of no place.     
So last Friday's session,       

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Jason also mentioned that       
there's a Pro Git ebook.        

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That's really great for you to  
learn some of the basics of     

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GitHub and the source control,  
some of the concepts.           

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It's a really good              
starting point for              

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you to learn those skills.      
I post a link here and          

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you can like check it out if    
you want. So there are three    

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main components in like Xcode   
9 Source Control Workflow, and  

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I will go through               
each of them briefly.           

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The first one is pulling and    
pushing. For pulling and        

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pushing is like dealing         
with your local changes and     

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the changes in the remote       
repository. So, for             

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clone and pull,                 

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you can download all the code   
from the remote repository to   

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your own laptop. Xcode 9        
actually make it really,        

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really easy to download         
a repository. You just click    

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the Clone and Download button   
and then open it in Xcode.      

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And Xcode will download         
all the changes for             

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you. It's really nice. And      

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I will show you how to do that  
in a demo. And another way to   

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do it is to copy out this       
GitHub repository address.      

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And I will also show you how    
to do that in a demo. For       

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the push, it's like you         
make some local changes,        

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you, and you want to push to    
the remote so that you can      

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edit it in another machine or   
share it to your friends.       

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So, every batch of code         
changes is called a commit.     

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The commit it's like            
a snapshot of all the code      

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changes and                     
also the description message.   

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It has the author, description  
message, and also the time.     

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I highly encourage you to       
make small commits instead of   

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making a really big commit,     
like only one commit for        

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the repository. That's          
like the final finish one.      

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Because making small commits    
makes it much easier to debug.  

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The rule of thumb is one        
feature at a time, and          

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each commit should              
be self-contained.              

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When bugs happen, you can       
easily revert to the previous   

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state without affecting         
the other files. So             

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here's what the commit panel    
looks like in Xcode 9.          

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You get the commit message      
here and also the author,       

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the branches,                   
the tags and remotes.           

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We will go through these        
concepts in a demo. And         

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here's the identifier,          
it is the SHA identifier for    

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this commit. The last           

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concept I'm introducing         
today is the branching. So      

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each little commits, one after  
one, is called a code branch.   

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In the GitHub repo,             
repository,                     

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the most important one is the   
master branch. You would wanna  

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always keep your master         
branch clean, bug-free and      

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stable. And when you want       
to work on new features,        

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you would like to branch        
from the master. So             

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Xcode 9 is really easy for      
you to just right-click and     

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create a new branch. The new    
branch will have the same       

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code as the master. But when    
you keep developing your code,  

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it won't affect the master      
branch. And after you finish    

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developing all your features,   
you've unit tested your code,   

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you can merge it back           
to master branch.               

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I will show you how to do the   
branching in this demo. So,     

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any questions so far? No,       

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so let's go into the demo.      
So let's pull out Xcode.        

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So before we do the fancy       
things in Xcode,                

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we would like to set up the     
GitHub account in Xcode. So     

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the way to do it as click       
on Xcode > Preferences          

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> Accounts. When you            
select the Add button,          

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you can add GitHub Enterprise.  
Enterprise is like,             

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when you work for a company,    
they will have the company      

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GitHub account. So              
I'm gonna select the GitHub.    

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And I'm using my Stanford       
email address. So               

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we've already signed in. And    
before we jump into the code,   

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we would wanna make sure the    
Source Control is setting up    

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correctly. So, these options    
is like, whether you            

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want Xcode to download          
the remote changes for you.     

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So that you won't need to pull  
the changes in command line.    

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And when you click on the Git   
button here, you can set up     

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some global ignored files. If   
you have used GitHub before,    

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you know that there's           
a gitignore file so             

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that your files won't be        
checked by the GitHub system.   

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So you can set up some global   
ignored files here. That means  

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like .D_Store files won't       
be checked by the GitHub. So    

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let's start by creating         
a new Xcode product.            

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Let's do Single View,           
and then GitTutorial.           

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And it's basically the same     
thing as we are doing when      

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creating the new project for    
our homework,                   

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but the difference is that we   
wanna select this button. So    

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this is the mysterious          
Source Control button we never  

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talk about in class.            

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And this means that Xcode will  
initialize a Git repository     

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for you. So we would select     
this button for this section.   

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Hit Create, and                 
then we would have              

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a Git repository, and           

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we can inspect the Source       
Control panel over here.        

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It's on the top left,           
and the second button.          

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It shows that we are currently  
at the master branch. And       

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the initial commit is just      
some free code given by Xcode   

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that create, initialize,        
and then push the code for      

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you. So,                        
let's make some change.         

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Maybe I will delete             
this free code. And             

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then add a print line.          

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And once I've saved the file,   
there's an M appeared here.     

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That M stands for modified.     
Basically, it means that your   

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local repository have some      
uncommitted changes. And        

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that's also modified in         
storyboard. I want to drag our  

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button. And                     

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put it in the middle. Okay,     

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let's save the change. So       
now I have made some change.    

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So we wanna commit              
those changes.                  

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It's like clicking              
the Source Control here, and    

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then hit Commit. Then           
a Version Editor will appear.   

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And it's really nice because    
you can see your change         

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side by side by clicking the    
filename. And it shows that     

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you've added one line and       
you've deleted some code.       

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And if you click on             
the button in the middle,       

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you can actually don't          
commit this specific line or    

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discards the change. So, let's  
also look at the storyboard.    

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Maybe it's your first time      
looking the storyboard.         

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At this level, we generally     
don't like added the file in,   

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in this level.                  
It's a XML file, so             

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it's super complicated. After   
you've confirmed that this is   

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the change you want, you would  
enter the commit message here.  

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Added a button and              
a print. Notice that            

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there's also a Push to remote   
button here. But we don't       

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have a remote now because the   
repository only lives locally.  

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We don't have a remote          
repository in the GitHub.       

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If we have the remote origin,   
we can push also to remote.     

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And I will show you how to add  
the remote origin in a second.  

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So now let's just               
commit the files. So            

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once I do that,                 
the M disappeared. And          

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let's go back to                
the Source Control Panel.       

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Look, here's the commit I just  
made. And you can inspect       

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it by clicking it and then      
select the button here. And     

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it shows the author,            
the date, the branches,         

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and also the files. If you      
want to inspect the changes,    

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you can actually click          
on the Assistant Editor.        

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I want my Assistant Editor      
on the bottom. And              

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then when I click the file,     
it actually                     

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displays the changes side by    
side. You can easily see what   

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files you've changed in         
this specific commit.           

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And let's make more             
changes here, like print,       

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hello CS193p.                   

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And over to Source Control      
button here, I can actually     

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discard all the changes         
in my current repository.       

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That basically roll back        
to the latest commit. But       

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I will show you how to revert   
to several commits ago.         

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So let's add this               
commit first.                   

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Add an, another print.          

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But we should have              
successfully committed because  

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there's no M over the           
ViewController. And say, for    

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this specific file, I want to   
roll back to two commits ago.   

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I can open this                 
Source Control button.          

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And then it's a side by side    
comparison between your         

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local revision and              
your commits. So                

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if I select the commit,         
two commits ago,                

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I can see all my changes.       
And I can click on the button   

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here, if I want to              
discard all the changes.        

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Revert, so                      
now my local repository         

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have reverted those changes.    

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That's commit. Revert.          

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Like I just mentioned,          

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all the code now lives          
in my local repository,         

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so there's no way I can share   
it to my teammate or work       

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on the other workstation. And   
also if I just lost my laptop,  

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everything will be gone.        
You certainly don't want that.  

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So let's see like how to        
add a remote. Origin for        

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this GitTutorial repo.          
And it's super simple here,     

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you just click on the Remote,   
and right-click.                

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There's a Create GitTutorial    
Remote on GitHub.               

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And it allows you               
to select public or             

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private repository. So since    
I'm using my Stanford account,  

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I can get the free              
private repo.                   

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Okay, now we have               
a remote origin, and            

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let's take a look. So           

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here's my                       
Stanford GitHub account.        

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And there's a GitTutorial       
repository we just created.     

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And it has all the files        
we've modified.                 

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And if you want to work         
in the other workstation,       

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you can just clone or download  
and open in Xcode and/or copy   

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the address. So before I        
show you how to clone,          

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let me show you how to add      
the collaborator. It's super    

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useful if you want to work      
with the other teammate. So     

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for this specific repository,   
you go to Setting,              

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and hit Collaborators.          

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And basically, you need to      
know your friend's GitHub ID,   

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and you just type it here.      
For demonstration,              

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I will add my personal          
account here. And               

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GitHub will you send an email   
to your friend and, or          

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you can just share              
this invite link.               

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Let me copy it here, and then   
sign into my personal account.  

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So I click on this link And     

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it says that you are invited    
to collaborate. So              

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I can accept the invitation.    
Now,                            

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I have the push access to       
this private repository.        

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So another way to create        
the repo is by cloning          

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the existing repo               
from the GitHub. Say,           

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I have a Concentration          
private repo here.              

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And I want to download          
it to my local machine.         

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I can just hit Open in Xcode,   
and Yes.                        

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So all the code were            
downloaded by Xcode. And        

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the other way to do it          
is save this address.           

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And then,                       

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in our Xcode welcome page,      

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you can select this Clone       
an existing project.            

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You can paste in the address,   
and then just clone.            

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So Xcode will do                
the exact same thing.           

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It's just copying all           
the files from remote.          

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The good thing is that in       
the source control panel here,  

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you can actually get all        
the code changes for            

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the repository. And             
you can also like inspect all   

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the changes you've made.        
So for                          

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this specific repo, actually,   
the master is a fully           

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functional version. The, I      
want to like work on the other  

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new features that may be,       
I think, is a little risky. So  

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I, I can branch from master     
by right-click here.            

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And I will call my new branch   
test because I don't have       

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better names.                   
So my current epository is set  

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to test. Now, it has the same   
copy of code as the master.     

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Let's work on some              
risky new features.             

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So that's to change the color   
of the button. Maybe I          

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think blue is too ugly.         
I want to change it to red.     

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And I commit this change.       

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Notice that because we          
have a remote origin,           

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we can actually select          
Push to remote. And             

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because the test branch only    
lives locally in my machine,    

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actually Xcode can create       
that remote origin test for     

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you. So                         
we can commit and push.         

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So in my current test branch,   
I have this changed. But        

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my master branch                
is not affected.                

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So, if you want to switch       
back to the master,             

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you can right-click on          
master and select Checkout.     

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Now my current branch           
is master. And when             

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I go back to the storyboard,    
the button is still blue.       

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Now say, you've fully tested    
your code, and you're saying    

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that the button should be red   
instead of blue in the master.  

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You can right-click here, and   

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then select Merge               
test into master.               

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The version editor is like for  
you to see whether this merge   

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is what you want.               
Another thing is that,          

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because the storyboard is the   
XML file, you would never want  

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to merge the same storyboard    
with the other teammates.       

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You can work on different       
storyboards, but                

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you would never like want       
to merge the change in          

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the same storyboard, because    
that's really, really painful.  

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Now we are at the master,       
and we also have the Changed    

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button color here. And when     
I go back to the storyboard,    

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The button is now red.          
So we've successfully merged    

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the change. And                 

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notice that our current         
master is ahead                 

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of the original master.         
So another way to push to       

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the origin is to click          
Source Control > Push.          

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Now all my notes are at         
the same snapshot.              

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Another cool thing I            
want to show you is that,       

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they make it really easy        
if you want to inspect your     

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commits. Like I have            
some commit for button.         

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It will show all the commit     
message that should,            

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has button in it. And           
you can also filter by author,  

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like author is junjie. And      

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you can also search last        
24 hours, last 30 days.         

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It's really helpful if you      
want to search your change.     

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So that's basically all for     
our demo.                       

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Do you have any questions? No,  

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okay, so that's it for today.   
Thank you for coming, and       

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good luck on your assignments.  
>> For more,                    

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please visit us                 
at stanford.edu.