git - How can I clean the history of / remove duplicate commits from my master branch? -

i'm trying clean old repository, may first 1 created when still learning how use git. looking @ history of master, noticed this:

r -- p -- -- b -- c -- d -- m -- e       \                      /        a' --- b' --- c' --- d' 

where a', b', ... same commits a, b,... m merge commit , e isn't last one.
there 2 branches in repository (master , develop), , master affected(develop has been created later).

i remove duplicate commits, p (exclusive) m, resulting in this:

r -- p -- -- b -- c -- d -- e 

how achieve that?

seems m merge of branch rebased version of same branch

i following:

git checkout master git rebase --onto d m 

this commands rebase commits m master branch tip on d (removing m history), since a' - b' - c' - d' reachable because of m, commits "removed" history , history end way looking for:

r--p-----a-----b----c----d----e

rebase powerful command, can amazing things :)