The purpose of this lab is to gain a workable knowledge of git. Not only is this a powerful tool for assuring you get the best grade possible on your projects, protecting you from losing code, and collaborating, but it is also a necessary skill in the work place.
You will never have a computer science job that doesn't require the use of a version control system.
For quick reference on the git commands we covered, see the cheat sheet [here] (https://github.com/PurdueCS190/lab6/blob/master/cheat_sheet.md)
This lab will walk you through an example project and teach you in a real use case situation how to use git and it's features.
Run this command to set up your working directory.
cd; curl -sL https://raw.githubusercontent.com/PurdueCS190/lab6/master/materials/setup.sh | /bin/bashBefore you start working you have to do some setup of git. You need to set up your global gitconfig with your name and email. These will be attached to each commit to tie you to them.
You should replace the $USER belowe with your real name, ie, "Scott Opell"
git config --global user.name $USER
git config --global user.email $USER@purdue.eduFor quick reference on git commands, see the cheat sheet [here] (https://github.com/PurdueCS190/lab6/blob/master/cheat_sheet.md)
You're given a project in CS 180 in which you have to create a Java program for traversing a family tree. Your program should be able to take a family in a given format and interact with the tree. You should be able to print out specific individuals in the family, groups of individuals, or switch context to a new individual. You can see a picture of the family tree below
![] (https://raw.githubusercontent.com/PurdueCS190/lab6/master/materials/tree.png)
We've provided you with the code already. Let's run it and see what it does.
- Navigate to the ~/cs190lab6/FamilyExplorer/ directory
- Run the command
$ bash compile.sh. - Now run
$ bash run.sh. - Enter
help. This command will print a list of available commands. Familiarize yourself with the project. (Bonus: Find bugs if you can!)
Now that we've got our project, let's get it in a git repository so we don't lose it before we have to turn it in.
Let's start by creating a new repository to contain our project.
- Run the command
$ git init. You should get an output that looks something like this:
Initialized empty Git repository in /u/data/u95/<your_username>/cs190lab6/FamilyExplorer/.git/
- Now enter
$ git status.
On branch master
Initial commit
Untracked files:
(use "git add <file>..." to include in what will be committed)
build/
compile.sh
run.sh
src/
nothing added to commit but untracked files present (use "git add" to track)
We have a new repository and we can see that git recognizes that there are new files. Before we make an initial commit, let's
add a .gitignore file. Recall that we don't want to commit .class files to a git repository.
- Run
$ echo -e "*.class\n*~\nbuild" >> .gitignore. This adds a line in the.gitignorefile to ignore files ending in.class, build, and DrJava buffer files (you will learn what these are when we talk about editors).
Now run $ git status again.
On branch master
Initial commit
Untracked files:
(use "git add <file>..." to include in what will be committed)
.gitignore
compile.sh
run.sh
src/
nothing added to commit but untracked files present (use "git add" to track)
We can see that the .gitignore file is there, but the build/ directory is gone! No more .class files!
Remember from lecture the staging area? Right now these files are untracked by git. This means that if we run $ git commit
now, no new changes will be commited. First we have to add these changes.
- Run the command
$ git add .This command adds all of the current working directory to be tracked by git. - Run the status command again. This time you should see a list of all the new files under "Changes to be committed:". We're ready to commit.
- Run
$ git commit -m "<your commit message>". Insert some message in the quotes. Your commit messages should be short, but descriptive and to the point. Say something like "Added initial source files."
For some hilarious git commit messages: http://www.commitlogsfromlastnight.com/.
Bonus: Explain to your lab TA how this website works.
Congratulations, you've successfully committed your files! Run $ git log to view your commit message.
Bonus: Why might it be good to do this step in two commits instead of one?
DON'T MOVE ON TO STEP 2 UNTIL YOU MAKE SURE YOU COMMIT YOUR CHANGES (check your git log).
Now that we've gotten our files committed, we'd like to make a change. Say we want the print output to be a little shorter and more concise.
Change the toString() method (line 71) in Group.java to look like this:
/** Override of toString() from superclass */
@Override
public String toString() {
StringBuilder output = new StringBuilder();
Formatter f = new Formatter(output);
for (Person p : group) {
f.format("%d: %s, ", group.indexOf(p), p.getName());
}
return output.toString();
}Change the toString() method (line 129) in Person.java to look like this:
/** Override of toString() from superclass */
@Override
public String toString() {
StringBuilder output = new StringBuilder();
Formatter f = new Formatter(output);
f.format("Name: %s, ", getName());
f.format("Age: %d, ", getAge());
String gender = getGender() == Person.MALE ? "MALE" : "FEMALE";
f.format("Gender: %s ", gender);
return output.toString();
}Recompile and run the project. Observe the differences in the output. Be sure to let your lab TA know right away if you are having compile or other errors. We don't want you to spend time debugging (at least not this week).
Let's check the status of our git repo.
- Run the status command. You should see that both
Person.javaandGroup.javashow up as modified under Changes not staged for commit: Now we need to add them to the staging area and commit - Run
$ git add src/Group.java src/Person.java. Now commit the files with a nice descriptive commit message. - Run
$ git logand you should now see both of your commits. You're well on your way to becoming a git pro!
DON'T MOVE ON TO STEP 3 UNTIL YOU MAKE SURE YOU COMMIT YOUR CHANGES (check your git log).
Now your CS 180 lab TA tells you that you need to add in support for printing and navigating to cousins. This is a serious new feature that could break things! With git you can feel confident that you won't lose the progress you've already made.
Add the following method to FamilyExplorer.java after line 63:
/** Get cousins */
private Group getCousins() {
if (current == null) return null;
Group cousins = new Group();
Person dad = current.getDad();
if (dad != null) {
Group sibs = dad.getSiblings();
if (sibs != null) {
for (Person sib : sibs) {
if (sib != null && !sib.equals(dad)) {
Group children = sib.getChildren();
for (Person child : children) {
cousins.add(child);
}
}
}
}
}
Person mom = current.getMom();
if (mom != null) {
Group sibs = mom.getSiblings();
if (sibs != null) {
for (Person sib : sibs) {
if (sib != null && !sib.equals(mom)) {
Group children = sib.getChildren();
for (Person child : children) {
cousins.add(child);
}
}
}
}
}
return cousins;
}Also add this case to the switch statement in FamilyExplorer.java on line 149 right above default:
case "cousins":
group = getCousins();
break;Recompile and try it out! Now you should be able to enter print cousins. Again, don't get stuck on this part.
If you are getting errors, ask a TA right away.
- Add the changes to
FamilyExplorer.java - Commit your changes.
You're getting fluent at these git commands already!
Pro tip: You can never overuse the log and status commands. You should be looking at these between almost every command
DON'T MOVE ON TO STEP 4 UNTIL YOU MAKE SURE YOU COMMIT YOUR CHANGES (check your git log).
Now that you're this far you decide that you want the output to be printed the way you had it before. First
let's look at our commit log. Run $ git log. Your output should look something like this:
commit a6bd3cc3ece612ee4ff1a343acfb36b90fcd5d32
Author: Levi Starrett <[email protected]>
Date: Sun Nov 2 23:51:05 2014 -0500
Added support for cousins
commit bfe63e9095f46ce522ac0033951090203a07fc31
Author: Levi Starrett <[email protected]>
Date: Sun Nov 2 23:46:22 2014 -0500
Changed output to shorter format
commit 179762b4273282d798b0df0dfc745620a79fffde
Author: Levi Starrett <[email protected]>
Date: Sun Nov 2 18:57:48 2014 -0500
Initial commit
We want to revert the commit that changed the output.
- Run
$ git revert <commit_hash>. This will open up an editor with a commit that says something like "Revert 'some message' This commit reverts some commit hash".
Important Note!
If it opens in vim, then follow these steps to save the file and return to the nice familiar terminal.
-
Don't panic
-
type
:wqFor the curious: the colon allows you to type commands, w is for write, and q is for quit.
-
You have now committed!
- Run the compile script and run the program again. It should be back to the old style of output.
Give your neighbor a high five, you just did some serious source control.
Show your TA your git log.
Here are some practical things you could do with git if you have extra time:
- Work on your .gitconfig file. Some useful information here: http://git-scm.com/docs/git-config
- Put your CS 180 project into a git repository! You can pretty much follow this lab to do so.
- Ask your TA a question about something you don't understand.