Introduction to git
version control for
serious hackers ;)
Alan Orth
Nairobi, Kenya
September, 2010
The Problem
- One project, many developers...
- Who fixed (or broke) what?
- Exactly which changes fixed (or broke)
feature X?
- How can we undo those changes easily (and
log them, so that we don't forget!)
The Solution
- Version control!
- Many solutions over the years...
- CVS (kitambo)
- Subversion (was very popular until git)
- Mercurial
- Bazaar
- I am biased, but git is the $%^!.
- Written by Linus Torvalds (… heard of Linux?)
git practice
$ mkdir test
$ cd test
$ git init .
$ git status
1. Create a new directory
2. Move inside the new directory
3. Initialize the new directory as a git repository
4. Show the current status of the repository
git practice
$ gedit hello.txt
Type “Hello World” then save and exit
$ git status
git shows hello.txt as “untracked”
Untracked files are files which are in the
current directory but are not under version
control!
git practice
$ git add hello.txt
$ git commit -m “Add hello.txt”
$ git status
$ git log
1. Add hello.txt to version control
2. Commit changes in current repository (-m tells
git to save a “commit message” with this commit)
3. Show status of repository
4. Show the commit log (a sort of history)
git configuration
Bio Sprint?! “Ammend” the last commit, telling git
who you are:
$ git commit --ammend --author=”Alan Orth
<aorth@cgiar.org>”
Make the settings permanent:
$ git config --global user.name “Alan Orth”
$ git config --global user.email a.orth@cgiar.org
Branching and merging
- master: the main “branch” of development
- Branches allow you to develop features and fix bugs
without polluting (or destabilizing) the master
- Many paradigms, but in git: branch early, branch often!
- Crazy idea you want to try? Make a branch! If
something breaks, just delete the branch :)
- Otherwise, “merge” the branch back into master...
Branching and merging
$ git branch goodbye
$ git checkout goodbye
$ git status
1. Create a new branch called “goodbye”
2. Switch to the new branch
3. Print out the status of the repository on the current
branch. Note the [goodbye ] in the top left... we are on
the “goodbye” branch!
Branching and merging
$ gedit goodbye.txt
$ git add goodbye.txt
$ git commit -m “Add goodbye.txt”
$ git checkout master
$ git merge goodbye
1. Put text in goodbye.txt and then save and exit
2. Add goodbye.txt to version control
3. Commit changes to the current repository
4. Switch back to the master branch
5. “Merge” the changes from the “goodbye” branch into
the current branch.
Getting Help
- Don't RTFM, it is confusing and technical
- Use google instead... there is always someone else
who has already tried to do what you're trying to do!
- Use git status frequently to see what's up
- Use git diff to see what changes have been made
- Use git branch to list branches in your repo
- Pro git: http://progit.org/
- Ask Alan?
A great, free ebook