Using git

For a more complete version of this document see Professor Newhall's page.

git is version control software. It is useful for managing code projects, particularly projects with partners. Using git, you will create a remote master repository (repo) for your project. You and your partners then each checkout (clone) a private local copy of the remote master repo, where you can add and commit changes to your cloned copy. To share local changes with your partners, you push them to the master to share with your partners. Any changes committed to a git repo can be recovered if lost.

This guide provides some basics for using git for CS lab work using Andy's 2014 setup31 and setup40 scripts for collaborative projects. It also has links to additional git resources.


Basics of using git for joint CS projects
The first step to using git is to set up a remote bare master repository for your shared project. Next, you and your partner clone local working copies into your own private subdirectories. Finally, you each commit changes to your local copies and push and pull changes to and from the remote master to share work.
This is mostly automated through the use of the setup31 and setup40 scripts. If you are enrolled in one of these classes, you can run the scripts and see which assignments and directories you can create.
[~]$ setup40

Usage: setup40 <assignment> <partner>

You need to specify the lab to setup
Here are available assignments to setup
examples  (Individual) 
projects/01  (Partner optional) 
For an individual assignment, you can run
[~]$ setup40 examples
Set up repo for examples
cd /home/adas/cs40/examples
to create/edit files
For a partner assignment, suppose Molly and Tejas are collaborating on a project. One partner, say Molly, should run
[~]$ setup40 projects/01 tejas
Once Molly's script has finished, Tejas can run
[~]$ setup40 projects/01 molly

Aside: First time users config settings

The setup scripts should take car of initial configurations for first time git users, but in case it doesn't, you may want to run the following commands. You only need to run these if git complains about your email or push default settings.
git config --global ""
git config --global  "Your Name"
git confit --global push.default simple
Replace the email and name strings with your email address and name. If you have not run these commands, then the very first git commit will fail and tell you to run them.

At this point, you now have a master git repository for your project that only you, your partners, and graders/instructors can access. All changes, additions, deletions, to this project can be done with git commands that will push and pull changes from this remote master copy.

Using your shared repo

You and your partner will work in your local private copies of the repo. You can add and commit changes to your private copy as you go, and choose when to push your change to the remote master repo. Once you push changes, your instructor or partner can then pull from the remote master into their copy.

An example of a sequence of common git commands:

 # check the status of your repo
 $ git status

 # see the changes to the file (compared to your last local commit):
 $ git diff blah.c

 # add a new file to the repo on the next commit:
 $ cp ~/private/foo.c .
 $ git add foo.c
 # or add new changes to an existing repo file to the next commit:  
 $ vi blah.c      # edit with your favorite editor
 $ git add blah.c  

 # commit your changes (adds and deletes) to your local repository:
 $ git commit

 # push committed changes from your local to the remote master repository
 #  note: the first time you push, you may need to do:
 #        git push origin master
 $ git push

 # your partner can now pull your changes from the remote into their local:
 $ git pull

Some notes about these commands:


It is useful to add a .gitignore file to your repo. It tells git automatically ignore adding certain files or file types to the repo, such as .o and executable files and editor backup files (like vim .swp files). This way if you do a git add git doesn't try to add all kinds of kooky files to the repo. Here is an example .gitignore file for a C program that build an executable file named myprog:
You add a .gitignore file to a git repo just like you add any other file:
git add .gitignore
git commit
git push

Common commands:

git help    # list common git commands  git help --all lists all commands
git add     # add changes or new files to the next commit 
git rm      # remove a file at the next commit
git commit  # commit your changes to your local repository
git push    # push your committed changes to the remote master repository
            # (note: the first time you may have to do: push origin master
git pull    # pull changes pushed to remote master into your local copy 
            # (git will try to merge changes into your copy)
git mv      # move a repo file
git diff    # see a diff between a file(s) and latest commit (local repo)
git diff master origin/master  # diff between your copy and master's
git status  # see what has changed between your copy and the master version
git branch -a # see all the branches (likely only master)

git tools:


git documentation sections 1 and 2 in particular are very useful
git user's manual
Andy's git wiki page more complete coverage of common and advanced git feature
git cheatsheet
git magic a good source of information about more advanced and obscure git functionality
converting cvs repository to git

Advanced git Features
See the git user's manual and/or git man pages (man git-clone, e.g.) for more commands.

git branches are a powerful feature of git but will not be used in CS31 and CS40 in Fall 2014.