Git: auto pull from repository?

Question

Is there any way to set up git such that it listens for updates from a remote repo and will pull whenever something changes? The use case is I want to deploy a web app using git (so I get version control of the deployed application) but want to put the "central" git repo on Github rather than on the web server (Github's interface is just soooo nice).

Has anyone gotten this working? How does Heroku do it? My Google-fu is failing to give me any relevant results.

Answer 1

Git has "hooks", actions that can be executed after other actions. What you seem to be looking for is "post-receive hook". In the github admin, you can set up a post-receive url that will be hit (with a payload containing data about what was just pushed) everytime somebody pushes to your repo.

For what it's worth, I don't think auto-pull is a good idea -- what if something wrong was pushed to your branch ? I'd use a tool like capistrano (or an equivalent) for such things.

Answer 2

On unix-likes you can create cron job that calls "git pull" (every day or every week or whatever) on your machine. On windows you could use task scheduler or "AT" command to do the same thing.

Answer 3

There are continuous integrations programs like Jenkins or Bamboo, which can detect commits and trigger operations like build, test, package and deploy. They do what you want, but they are heavy with dependencies, hard to configure and in the end they may use periodical check against git repository, which would have same effect like calling git pull by cron every minute.

Answer 4

As some have noticed after trying this, if you use php exec(), it turns out that solving for permissions is not that simple.

The user that will execute the command might not be your own, but www-data or apache.

If you have root/sudo access, I recommend you read this Jonathan's blog post

When you aren't allowed/can't solve permissions

My solution was a bit creative. I noticed I could create a script under my username with a loop and git pull would work fine. But that, as pointed out by others, bring the question of running a lot of useless git pull every, say, 60 seconds.

So here the steps to a more delicate solution using webhooks:

• deploy key: Go to your server and type: ssh-keygen -t rsa -b 4096 -C "deploy" to generate a new deploy key, no need write-permissions (read-only is safer). Copy the public key to your github repository settings, under "deploy key".
• Webhook: Go to your repository settings and create a webhook. Lets assume the payload address is http://example.com/gitpull.php
• Payload: create a php file with this code example bellow in it. The purpose of the payload is not to git pull but to warn the following script that a pull is necessary. Here the simple code:

gitpull.php:

<?php

/* Deploy (C) by DrBeco 2021-06-08 */

echo("<br />\n");
chdir('/home/user/www/example.com/repository'); 
touch(GITPULLMASTER);
?>

• Script: create a script in your preferred folder, say, /home/user/gitpull.sh with the following code:

gitpull.sh

#!/bin/bash

cd /home/user/www/example.com/repository
while true ; do
      if [[ -f GITPULLMASTER ]] ; then
            git pull > gitpull.log 2>&1
            mv GITPULLMASTER GITPULLMASTER.`date +"%Y%m%d%H%M%S"`
      fi
      sleep 10
done

• Detach: the last step is to run the script in detached mode, so you can log out and keep the script running in background.

There are 2 ways of doing that, the first is simpler and don't need screen software installed:

• disown:

  • run ./gitpull.sh & to put it in background
  • then type disown -h %1 to detach and you can log out

• screen:

  • run screen
  • run ./gitpull.sh
  • type control+a d to detach and you can log out

Conclusion

This solution is simple and you avoid messing with keys, passwords, permissions, sudo, root, etc., and also you prevent the script to flood your server with useless git pulls.

The way it works is that it checks if the file GITPULLMASTER exists; if not, back to sleep. Only if it exists, then do a git pull.

You can change the line:

mv GITPULLMASTER GITPULLMASTER.date +"%Y%m%d%H%M%S"`

to

rm GITPULLMASTER

if you prefer a cleaner directory. But I find it useful for debug to let the pull date registered (and untracked).

Answer 5

For our on-premises Windows test servers, we use Windows Task Scheduler tasks, set to run every 3 minutes, pulling from Bitbucket Cloud to repositories on those servers. While not instantaneous, it meets our needs, and has proven to be reliable.

Answer 6

I know this question is a bit old, but you can use the windows log and git to autopull your project using a webhook and php (assuming your project involves a webserver. See my gist here : https://gist.github.com/upggr/a6d92e2808e9628ebe0d01fd93569f4a