cs190lab5

Before starting lab5, it is highly recommended that you review the Git Reference Sheet. Not all commands will be given to you and the document above has the ones you will need to complete this lab.

The slides for "Git Basics" can be found here. Git Basics

The main part will utilize the core git commands you've learned in order to create a new repository, add files, commit them, and push them up to your github.

There is a bit of setup required that you must do this first.

What You'll Learn

By the end of this lab, you'll know how to create a git repository, add files to it, make changes, push everything to github, and how collaborate effectively using git and github.

Setup

Depending on your working environment, perform the appropriate action:

Environment	Action
Linux Lab Machine	Open a terminal window
Windows or Personal Computer	SSH into `data.cs.purdue.edu`*

* You must have X11 forwarding enabled. If you are on the Windows Lab Computer, follow the instructions below:

Search for 'Xming' in the start menu and run it.
Open PuTTy
Expand the 'SSH' tab from the 'Category' list
Choose 'X11' from 'SSH' list
Check 'Enable X11 Forwarding'
Connect like normal to data.cs.purdue.edu within PuTTy.

Required Git Setup

You need to set up your global gitconfig with your name and email. These will be tied to each commit so that it is known who committed the code.

# replace 'Scott Opell' with your own name
git config --global user.name "Scott Opell" 
  
# replace 'me@scottopell.com' with your email
git config --global user.email "me@scottopell.com"

We will want to use a global gitignore file, so we don't have to deal with vim swap files, DS_STORE files, or java class files. The command below copies the gitignore file from this repository into your home directory

wget -O ~/.gitignore_global https://github.com/scottopell/cs190lab5/raw/master/gitignore_global

Now we need to tell git where the global ignore file is

git config --global core.excludesfile ~/.gitignore_global

Run the command below. Don't worry about what it does. It sets the settings of git to the safest options.
```
git config --global push.default simple
```

Creating, Committing, and Pushing

In your home directory, create a new folder named cs190lab5_<your_username>. Ex. I would create a folder cs190lab5_sopell.

mkdir ~/cs190lab5_$USER

You will then cd into the directory created above and initialize a new git repository.
```
cd ~/cs190lab5_$USER
git init
```
Download this template file LabTemplate.java into the repository you just created

wget -O ~/cs190lab5_$USER/LabTemplate.java https://github.com/scottopell/cs190lab5/raw/master/LabTemplate.java

add this file to the repo

git add <filename>

commit this file to the repo

git commit -m "<commit message>"

Log in to GitHub.com using the account you made for cs180
Click the Create a New Repository button.

Enter in a "Repository name" (cs190lab5_<username>) and click "Create Repository"

Make sure NOT to check the box that says "initialize this with a readme"

This is fine when you're doing this on your own, but for this lab, commands will not work as expected

Copy to your clipboard the URL in the yellow box titled "Quick Setup"
In your local git repo (cs190lab5_<username>), add the github URL given as a remote.
```
git remote add origin <git URL here>
```
Do your initial push
```
git push -u origin master
```

Note that the above two commands come straight out of the "repository created" page on github. You will be prompted for a username and password here, use your login information for github

Go to the repo settings

Add your partner as a collaborator

Stop here and wait for your partner for finish this section

Collaboration

Clone your partner's repository into your home folder

cd ~
git clone <his/her_git_URL_here>

This creates a folder in your home directory with the name of his/her repository name.

cd into your partner's repository
In your partner's repository, compile and run LabTemplate

 javac LabTemplate.java
 java LabTemplate

It will fail because we have an invalid URL (https://example.com) inside LabTemplate.java.

Open up your partner's LabTemplate.java with gedit and find the line with String URL = "https://exammple.com".
Replace the URL with one of the two following URLs

https://api.github.com/zen
           or
https://api.github.com/octocat

Now save this file, compile and run again using the above commands. You will now see some output from it.
While still inside your partner's repository, you will commit these changes and push them up to their repository

git commit -am 'message here'
git push origin master

Wait again, for your partner to catch up and finish this section

Merge Conflict

Now, cd into your own repository.
Open up your own LabTemplate.java in gedit.
The file will contain the https://example.com URL. Your parter has committed a change to your own repository. Ask him which URL he/she has used.
You need change the URL variable inside LabTemplate.java to other URL, the one that your partner did not use when he made changes to your repository.
Commit your changes using the same syntax as above.
Try to push your changes with

git push

NOTE: This WILL cause an error, that's okay, read on to the next step

Git will tell you that there are new commits on the remote, so you need to pull them before you can push any of your commits.

git pull

Git will tell you that there are merge conflicts LabTemplate.java
You need to now open up LabTemplate in an editor of choice, and look for the section resembling the following

 // We need to ensure that we use a URL that starts with https
 // the s is important
<<<<<<< HEAD
 String URL = "https://api.github.com/zen";
=======
 String URL = "https://api.github.com/octocat";
>>>>>>> 581ac725455f2c8aef02a48dc5e45e44ccef69f1
 // We can print out the contents of any https site now!
 System.out.println( enlightenMe(URL) );

We want to keep our changes, not our partners, so we will delete the content in between ====== and >>>>>>> and the other merge markers. Your code will now look like you would expect, something roughly similar to this.

 // We need to ensure that we use a URL that starts with https
 // the s is important
 String URL = "https://api.github.com/zen";
 // We can print out the contents of any https site now!
 System.out.println( enlightenMe(URL) );

We need to tell git that we have a version of LabTemplate.java that we like, so please add LabTemplate.java.
commit these changes.

For a commit that fixes merge conflicts, its common practice to use a message similar to "fixes merge conflicts on LabTemplate"

Push these changes up to your remote repository (github) and verify that you can still compile and run LabTemplate.

You have now created a repository from scratch, added, committed, pushed, pulled and fixed your first merge conflict!

Grading

Before raising your hand to be graded, open up your repository on github and open it to the "network" tab. This is right above the settings tab from earlier.

scottopell / cs190lab5