You will have to clone the repository first, thus your first step was
Git.cloneRepository().setURI( remotePath ).setDirectory(
To just checkout a commit by its id you can call
git.checkout().setName( "<id-to-commit>" ).call();
But note that this will result in a detached
HEAD. To avoid this, you can tell
checkout to create a new
branch first that points to the commit and then checkout this branch.
git.checkout().setCreateBranch( true ).setName( "new-branch"
).setStartPoint( "<id-to-commit>" ).call();
The API isn't very intuitive, but it does what it should.