I know this may be late, however I have noticed that it only occurs if I make a commit to a branch is a bit more updated than the branch that i'm merging.
It turns out that if I change a branch (i.e., add more files to the branch), and try and merge another branch into it, Git will request me to write a
MERGE_MSG for that branch.
In this image, it shows that I added a LICENSE file in
master and a
.gitignore file in branch
master contains a new file, LICENSE, and
npm-init does not know about it, Git asked me to write a message about why I should merge it.
Similarly, I merged
add-dev before I merged the changes in
I know this may be hard to understand (even for me at first), but I hope the image clears things up :)