Initial state:
==============

A - B - C - D - E - F - G - H  origin/master
             \
              \
               I - J - K - L  master


MERGE: After 
a) git pull
b) git fetch && git merge origin/master:
========================================

A - B - C - D - E - F - G - H  origin/master
             \               \
              \               \
               I - J - K - L - M  master


REBASE: After 
a) git pull --rebase
b) git fetch && git rebase origin/master:
=========================================

A - B - C - D - E - F - G - H  origin/master
                             \
                              \
                               I' - J' - K' - L' master