Conflicts are going to happen if both branches have changes to the files. This is a good thing. Keeping your branches up-to-date with each other will prevent some of them
. However over all, conflicts are not bad. The rebase option can also prevent many of them from happening.
git merge branch_1
If you are on master, merging will bring the changes as you expect.
http://www.kernel.org/pub/software/scm/git/docs/git-merge.html
You could also
git rebase branch_1
This will take the changes from branch_1 and append them to master without a merge commit.
http://www.kernel.org/pub/software/scm/git/docs/git-rebase.html