You’ve decided that you’re going to work on feature_12 as an example. To create a new branch and switch to it at the same time, you can run the git checkout command with the -b switch:
$ git checkout -b feature_12
Switched to a new branch "feature_12"
This is shorthand for:
$ git branch feature_12
$ git checkout feature_12
After you are done with your branch editing, commit your code to your branch.
$ git commit -a -m 'added a new feature name [feature_12]'
Merge your branch work into master.
$ git checkout master
Switched to branch 'master'
$ git merge feature_12
If there is any conflict, you should solve in your local branch before merge into master!!!
If all goes well, delete your feature branch. Always start a new branch for a new feature.
$ git branch -d feature_12
Deleted branch feature_12
Let me know if there is any issue.