How can I see a "three way diff" for a Git merge conflict?

Question

Suppose I'm on Git branch master and I git merge featurebranch. There is a conflict in foo.html.

When I open foo.html, I see, in the area of the conflict, what master has and what featurebranch has. But I can't really tell what change was made on master that conflicted with featurebranch; I only know what master has now.

I'd like to see the diff that each one applied.

Or, to get the same information, I could see:

• The version master has now
• The version featurebranch has now
• The version their common ancestor had

How can I see this?

Answer 1

From git-merge(1),

An alternative style can be used by setting the "merge.conflictstyle" configuration variable to "diff3".

In addition to the <<<<<<<, =======, and >>>>>>> markers, it uses another ||||||| marker that is followed by the original text. ... You can sometimes come up with a better resolution by viewing the original.

This can be enabled using

git config --global merge.conflictstyle diff3 

or right in ~/.gitconfigfile

[merge]   conflictstyle = diff3