What we want to achieve:

• one click create a working version of rails project on DigitalOcean
• set up a local working version of the project
• set up remote & local git repo so we could push to update remote rails project folder
• and deploy automatically with push

Step 1: One Click Create Droplet

On digitalocean’s create droplet page, go to the Applications tab, select Ruby on Rails on 14.04 (Postgres, Nginx, Unicorn), and hit Create.

Step 2: Server Side Git Setup

# ssh log onto your droplet and go to the rails root folder:
$ ssh [email protected]
$ cd /home/rails/

# configure git
$ git config --global user.email "[email protected]"
$ git config --global user.name "YourUserName"

# create an empty folder and git initialise it as a bare repo
$ mkdir rails_project.git
$ git init --bare rails_project.git

# git initialise the existing rails folder as a normal repo
$ cd rails_project
$ git init
$ git add .
$ git commit -m "init commit"

# link the repos together, use bare repo to track upstream one
$ git remote add origin ../rails_project.git
$ git push -u origin master

Step 3: Server Auto Deploy Setup

Set up auto deploy with git hook. We’re using the post-receive hook, which runs after the entire update process is completed. It can also be used to update other services, like running auto installs.

$ cat > /home/rails/rails_project.git/hooks/post-receive

Paste these lines in, and then press Control+D to exit.

#!/bin/sh

echo "-----------------------------------"
echo "Post receive hook: Updating website"

export GIT_WORK_TREE=/home/rails/rails_project
export GIT_DIR=/home/rails/rails_project.git

cd $GIT_WORK_TREE
sudo -u root git pull
sudo -u root git checkout master -f

Then make it executable by:

$ chmod +x /home/rails/rails_project.git/hooks/post-receive

Step 4: Local Git Setup

If you don’t have Ruby or Rails locally yet, follow this and have Ruby as well as Rails set up. After which, 

# pull from your remote git repo with:
$ git clone ssh://[email protected]/home/rails/rails_project.git

# install gems
$ cd rails_project
$ bundle install

Step 5: Configure Postgres database

If you haven’t already got postgres installed,

# install postgres
$ brew install postgres

# create database
$ initdb /usr/local/var/postgres

# auto launch on login
$ mkdir -p ~/Library/LaunchAgents
$ ln -sfv /usr/local/opt/postgresql/*.plist ~/Library/LaunchAgents
$ launchctl load ~/Library/LaunchAgents/homebrew.mxcl.postgresql.plist

Now that you have postgres installed, go to rails_project/config/database.yml and edit the following line:

# in the first block, change the username to your own username on mac.
# note that case matters here.
default: &default
 ...
 username: your_username_on_mac

In Terminal,

# create and migrate local database
$ rake db:create:all
$ rake db:migrate

Final Step: Enjoy.

# finally, run rails run!
$ rails server