I cloned the master and started doing he my work . Due to permissions I push the branch to my fork . I then sent a pull request to my master and someone with permission does the merge . I notice that Github.com creates a merge commit snapshot which to me looks like just a diff of the entire changes which is actually not necessary but helpful in the sense I can just look at merge commit to see the entire diff . I can see the same sha has as my own branch - hence it looks like the merge is an extra commit which probably aint nexeccary since its a fast forward ?

master - a
myfork(computer) - a->b->c
myfork(github) - a->b->c

Pull request myfork - master (which it says I can automatically merge) shows the entire diff and then when I merge it , it shows up as master - a->b->c-d . The d is a merge commit which I think it not really required because it is a fast forward ? Can someone explain why does this happen ? I think this is the same scenario if I rebase master if master had gone ahead , but that has not happened . Master is still at when I merge .