Git for dummies

The basics: What you need to know

Setup

Set up your system:

 sudo apt-get install git-core
 git config --global user.email somebody@somewhere.tld
 git config --global user.name "John Doe"

Note that if you are using debian etch, you will need to get a backport of git from backports.org.

Getting the repo

Get a copy of the library project (assuming the central repository is on a server named dev.freegeek.org):

 git clone dev.freegeek.org:/git/library
 cd library/

Sort of like svn update:

 git pull

Like svn update (but if you have local commits):

 git fetch
 git rebase origin/master

(Master is like trunk is in svn.)

Making changes

Now edit a file

 vi TODO 

(See it's just like svn!!)

Now schedule this modification to be committed locally:

 git add TODO 

Want to see changes that you hain't yet git added?

 git diff

Want to see what you are about to commit?

 git diff --cached

Now commit it locally:

 git commit

Now, if you want to commit all of the changes you've made, but don't want to "git add" a million files, you can shorted it to this:

 git commit -a

The -a tells git to commit "all"

If you screw up changes to a file, and just want to put it back:

 git checkout myfile

think of checkout (when used like this) as the git equivalent of "svn revert".

Now send your locally committed changes to the main repository:

 git push

Cool toys: What you want to know

also known as "candy for the coders".

cool settings

TODO

git-rebase -i

TODO

keeping a fork

TODO

reverting a commit

yes, you can rebase out a commit. But never make changes to commits that have already been pushed. The correct way to "undo" a pushed commit is to do this:

 git revert SHA1_HASH_GOES_HERE

git-add -i

TODO

repository maintenance: taking out the trash

TODO

Complicated stuff: What you really don't want to know

Referencing a commit

TODO

Wtf is a refspec

TODO

Branches

TODO

Creating a new remote branch

To push your local branch, A, to a new (not yet created) remote branch, B, do this:

 git push origin A:B

Most of the time, you'll just want to do this:

 git push origin master:master

After you push a local branch to a new remote branch, if you want your local branch to automatically know to pull from it, run this:

 git config branch.$(git branch | awk '/^* /{print $2}').remote origin; git config branch.$(git branch | awk '/^* /{print $2}').merge $(git branch | awk '/^* /{print $2}')

That looks complicated, but it isn't. I just added a bunch of awks so that it automatically works on the current branch. The way that you would normally do it is like this:

 git config branch.A.remote origin; git config branch.A.merge B

where B is the remote branch, A is the local branch, and origin in the remote (origin is the default created when you clone from somewhere).

Merging

TODO: explain how to merge

If you are going to merge something, for now make the changes in the branch, then merge it into trunk. This way it is tracked correctly. While cherry-pick can be used to get one commit from trunk into the branch, it does not track it as a merge.

Tags and all the associated evil

TODO

The evil: once you push a tag, it's final. you can push a new version of the tag, but anybody who has already fetched the tag will not even know about the change. When you screw up a tag, you have to either send out an email instructing people to delete the tag and refetch it or use a different tag name. Not a good thing to do. There is reasoning behind this, though. Git is targeted towards security, and works by the concept that if you know the 40 character SHA1 hash of the most recent commit, you can trust the entire tree of commits.

The index

So, with git you have multiple places where changes are "kept":

• remote repository
• local repository
• the index
• your working copy

The index is where you "stage" changes you are about to commit. git-add takes changes from your working copy and updates the index to match (this was called git-update-index in previous versions of git).

After you edit the file (in your working copy), there are a few steps to get it to the remote repository.

From working copy to index:

 git add file

From index to local repository:

 git commit

From local repository to remote repository:

 git push

Other resources

• Git - SVN Crash Course - A good beginners tutorial
• Git (software) - Wikipedia, the free encyclopedia - Explains a lot about how git works