[Freeswitch-users] How to realize -GIT pull latest version to a local copy and work with prevoius changes

I'm a newbie with GIT, a few months ago, i use git to pull the Head to a local copy and then on this copy i change some code, e.g. 'my test code' insides a lots of files. now i found previous copy has some bugs and latest head fixed it, so i want to pull out the latest Head, however, meanwhile i want to keep my previous changes, is it doable? if not, i have to pull the latest Git to another local copy and on this copy i have to manually rewrite my changes in all of relative fiels, it will be a heavy workload (my god ), would somebody can help how to minimize the manual work load to realize it, thanks in advance! P.S. i'm using 'Git Extensions' as git tool on windows platform... Regards. Charles 2011-04-01 Charles