How can I preview a merge in git?

I have a git branch (the mainline, for example) and I want to merge in another development branch. Or do I?

In order to decide whether I really want to merge this branch in, i’d like to see some sort …

Changing git conflict markers

Is it possible to change the conflict markers to something user defined?

Motivation:

It has happened several times to me that, due to hasty and not very careful merging of several branches, there …