After i change something in my local source, how can i revert to the latest official source....So i want to be able to get the latest "revision", apply a patch, compile, test, revert changes so i can apply the next patch.
That's actually something git excels at, as it has cheap local branching. So you just create a new branch e.g. 'testpatch' based on the current master. Apply the patch, build and test it. After it's done you can either discard the branch or commit and rebase it on top of master.
Basically this comes down to:
git checkout -b testpatch
git apply ./foo-bar.patch
[build]
[done testing]
git checkout master
the you could either delete the 'testpatch' branch
git branch -D testpatch
or apply it's changes
git rebase testpatch
git branch -d testpatch