There is no such thing as "automatic merge". A merge conflict happens when two humans have made "incompatible" changes. A human must manually decide what changes to keep. The command to run is:
git mergetool
This will bring up an editor highlighting the conflicts.
I also recommend setting up a gui to edit the changes. There are many options, this one is as good as any:
Setting up and using Meld as your git difftool and mergetool - Stack Overflow[
^]
A good way to reduce conflicts in the future is if all team members update their local branch AND merge as often as possible.