Automated git push deployment

Method and scripts to deploy to a remote repository which can also be directly modified.

Why?

Many methods using a git bare repository exist and allow deployments through git push, but they fall short when the remote content must also be modified by other means.

Such a situation should not arise in a traditional development environment. Nevertheless, there are cases where it does. There are even cases where the software itself is designed in this way. Flat file CMS are such an instance.

How it works?

The remote - let us call it production - has two repositories:

• bare
  special repository that allows us to push to it
• live
  live application repository with the actual files (worktree)

To deploy from a local repository:

1. We push to production, more precisely to bare.
2. The hooks on bare check the state of live:
   • if there are modifications, they are pushed to bare;
   • if there are no modifications, our push is accepted and live pulls from bare.

Map

Process flow

Prerequisites

• git installed locally
• git installed on remote
• access to the remote through SSH for deployments with git push

Setup

1. Production

1. Create the bare repository:

   git init --bare bare.git
   

2. Copy the content of bare.git to the newly created directory.

3. Add execution permissions:

   chmod +x deploy-config.sh
   chmod +x hooks/pre-receive
   chmod +x hooks/post-receive
   

4. Create the live repository where your application should be located:

   git init
   

5. In live, add bare to remotes:

   git remote add bare /path/to/bare.git
   

6. Edit deploy-config.sh according to your setup.

2. Local

1. If no local repository exists, create one:

   git init
   

2. Add production to remotes, more precisely its bare repository:

   git remote add production user@yourserver:/path/to/bare.git
   

Usage

When everything above is set up, and provided that an SSH connection can be established with the remote server, we can deploy from the local repository with:

   git push production master

Pull from live without pushing

Directly pulling from live is impossible, as git does not have any fetch or pull hook.

If you absolutely need to pull from live without pushing any commit, there is a method that only works if changes were made to production since the last commit (otherwise your dummy commit will be register on production):

1. make a dummy commit (touch dummy);
2. push it to production;
3. if as expected new work was made on live, the push is rejected and both production repositories get synchronized;
4. cancel the dummy commit (git reset HEAD~1 ; git clean -f)
5. pull from remote

Notes

• There are no cron jobs involved.
• For a push to be accepted, bare and live must be synchronized.
• bare and live are automatically synchronized on each push trial.
• You cannot directly pull new work from live (see: Pull from live without pushing);
• This setup is not a replacement for a backup system.