This is a quick document to show what is the difference between git rebase and
git merge.

Here is your situation:

                     A---B---C topic
                    /
               D---E---F---G master

Now if you rebase topic to master, you'll get:

                             A´--B´--C´ topic
                            /
               D---E---F---G master

and if you merge master to topic, you'll get:

                     A---B---C---H topic
                    /          /
               D---E---F---G master

where H is a merge commit. (It will have two parents: C and G.)

Merge is done by git pull (it's git fetch + git merge). This is usually what
upstream does. You don't want to merge when you maintain a patchset.

You want git fetch + git rebase.

NOTE: This will rewrite your history, so people should not clone your branch.
Though this is not a big problem, usually people won't clone your code till it
isn't merged. :)

See also http://git.or.cz/gitwiki/GitFaq#head-1168c3027a2b7060df8c5cf141756c8e0e33139c