.gitconfig

[alias]
  up   = !sh -c 'git checkout master && git pull && git merge $0 && git push && git checkout $0'
  down = !sh -c 'git checkout master && git pull && git checkout $0 && git merge master'

down.sh

# down: updating feature branch from remote master

git checkout master
git pull
git checkout $1
git merge master

gistfile3.txt

git config alias.ci commit

or edit $HOME/.gitconfig

[alias]
        ci = commit

up.sh

# up: pushing feature branch changes to remote master

git checkout master
git pull
git merge $1
git push
git checkout $1