I have two git branches with different content. Why doesn't git merge them? It says, "Already updated."

I have a branch master

and another_branch

with twice as many files.

How come when I git checkout master

then git merge another_branch

it says Already up-to-date.

and doesn't merge additional files into master

?

(Yes, I already did git add .

, while I crossed it out another_branch

. git commit

Says there is nothing to do.)

I have already seen this post and this post, but so far nothing has worked.

EDIT: The branch master

has files, and the branch another_branch

has the same files and more. Why won't these additional files be merged?

EDIT: I solved the problem by copying the files from another-branch

to the external folder, checking master

, copying the files back from the external folder and adding all the new files and making a new commit.

Think about it, I think if I made a small change in another_branch

and then committed, I could merge everything into master, but I couldn't try it.