You should not use the 'pull...' command for "going back to" (checking out) an older version of your code.
The 'pull' and 'push' commands are used for synchronizing your local repository with an "origin" remote repository. This feature is normally used when you 'clone' an original remote repository in order to coordinate your changes with other programmers.
If you created your project from scratch, you won't have any remote repository to push to or pull from.
Back to the original question, as far as I know, Xcode 4 won't let you to checkout older commits within the user interface, unless you created a new branch for that commit. Nevertheless, you can do it from the command line. For that, use the following command from your project folder
$ git log --format=oneline
to get the hash code of the commit you want to go to, and then use:
$ git checkout desired-hash-code
to checkout that particular version. Once there, you can make tests, changes, and possibly create a new branch. If you do a commit without creating a new branch, you will lose the newer commits in your current branch. If you want to go back to the newest commit after having performed some tests on your older version use:
$ git checkout master
note again that this won't work if you do a new commit from your old code version without creating a new branch, because newer commits in the current branch get dereferenced.
If you are new to Git, I would read any of these documents:
I would also like to highlight these two:
Cheers.
与恶龙缠斗过久,自身亦成为恶龙；凝视深渊过久,深渊将回以凝视…
