I'm going to give the basic answer and the advanced answer.
Basic answer: after you do a pull, go to File->Source Control->repositories. You then can click on your repository and see all the commits that others (and yourself) made. There's a little disclosure triangle next to each commit. Clicking it will show you the list of changed files. Clicking on the "show changes" button will allow you to examine the details of each change.
Advanced answer:
You're going to have to learn to operate a bit different with git and it's going to seem foreign to you since you're used to the subversion way of doing things. Stick with it though. Git is awesome once you get the hang of it.
First things first. When you want to retrieve changes from the central repository (github), you have two choices on how to do that. You can fetch or pull. With fetch, the changes are pulled into your local repository, but not merged until you say so. With pull, the changes are downloaded and merged in one step. Many people assume that pull is the better choice, since it accomplishes both tasks in one step.
However, using pull makes it a little more difficult to see what happened, unless you have a decent knowledge of git commands.
To see what changed, do the following from Terminal:
git checkout master
(Make sure we're on the master branch)
git fetch
(This command pulls down the changes, but keeps them in their own <remote_name>/<branch name> branch until you explicitly merge them)
git diff origin/master
(This command shows you the differences between what you just pulled down and your local copy of master)
You can also use the git difftool command (if you have it configured) to see the differences in a graphical tool like FileMerge.
Once you've review the changes and are satisfied, to bring them into your local branch, you'd do:
git merge origin/master
(merge origin/master with the branch I'm on - master)
This process gives you the flexibity to examine things before they're merged. If you're not happy, you might want to have a developer revert his change for example.
Now, it's possible to do all the same with git pull, but since the changes are merged automatically, it makes it a bit more complex. For example, after pulling, to see the diff you'd have to figure out what your commit ID was prior to the pull and then do:
git diff <id of commit before pull>..
Same result, just a little more complex.
The nice thing about git though is that it tries REALLY hard to keep from losing any of your data. So, for example if you git pull and don't like the changes, you can do a git reset --hard <commit of the last good commit> and you'll be right back to where you where.
Learning to do these things from the Terminal may seem difficult, but it gives you tremendous power so it's worth the effort to learn.
