------------
$ git checkout topic
- $ git pull . master
+ $ git merge master
o---*---o---+ topic
/ /
------------
$ git checkout topic
- $ git pull . master
+ $ git merge master
$ ... work on both topic and master branches
$ git checkout master
- $ git pull . topic
+ $ git merge topic
o---*---o---+---o---o topic
/ / \
------------
$ git checkout topic
- $ git pull . master
+ $ git merge master
$ git reset --hard HEAD^ ;# rewind the test merge
$ ... work on both topic and master branches
$ git checkout master
- $ git pull . topic
+ $ git merge topic
o---*---o-------o---o topic
/ \