# assumption: a project called `repo` already exists on the machine, and a new branch has been pushed to GitHub.com since the last time changes were made locally
# change into the `repo` directory
cd repo
# update all remote tracking branches, and the currently checked out branch
git pull
# change into the existing branch called `feature-a`
git checkout feature-a
# make changes, for example, edit `file1.md` using the text editor
# stage the changed file
git add file1.md
# take a snapshot of the staging area
git commit -m "edit file1"
# push changes to github
git push
