July 19, 2016

How to setup a git repository to post commit notifications to Slack

This article explains how to install a bash script that posts a new message into a Slack channel when commits are pushed to your project's git repository.

Note that this implementation does not require the usage of GitHub, but you may also utilize local git repositories hosted on your own server.

Create a bare repository

To create a new repository on your server named foo.git, first connect to your server, then run the following commands

# Navigate on your server to the desired repository location
cd /desired/path

# Create the directory
mkdir foo.git

# Navigate inside the new directory
cd foo.git

# Initiate a bare git repository
git init --bare --shared=2664

Using the --bare flag ensures that the repository only contains the version control information and doesn't have any local files. This is necessary to be able to clone and push to the repository. Setting --shared=2664 sets the core.sharedRepository setting, which forces git to do all new file creation with 2664 permissions. This helps to avoid issues with multiple users pushing to the repository.

If the foo.git repository already exists and you need to fix the permissions after-the-fact, perform the following commands

# Navigate to the repository
cd /path/to/repo/foo.git

# Apply fixes
chgrp -R swdev * #may require sudo
chmod -R ug+rws * #may require sudo

Next, edit the file /path/to/repo/foo.git/config. Under the [core] area, add or modify the following line

sharedRepository = 2664

Install script on the server

Download the bash script to your local machine.

Copy the file from your local machine to your project with the following command

# Run command from your local machine (not on your server)
scp ~/local/path/to/file/post-receive @servername.com:/repo/path/on/server/foo.git/hooks/post-receive

Finally, change the permissions of the post-receive file on the server to allow it to be executable

# Navigate to the repository's hooks folder on your server
cd /path/to/repo/on/server/foo.git/hooks

# Change permissions of the post-receive file
chmod +x post-receive

Configuration

Add an incoming WebHook to your Slack team

Make note of the WebHook URL https://hooks.slack.com/services/...

Connect to your server and navigate to your repository. Add the WebHook URL via git config along with two other settings

# Navigate to repository
cd /repo/path/on/server/foo.git

# Add WebHook URL
git config hooks.slack.webhook-url 'https://hooks.slack.com/services/...'

# Set option to show all commits pushed
git config hooks.slack.show-only-last-commit false

# Set repository nice-name
git config hooks.slack.repo-nice-name 'Our Awesome Project'

Options

Listed below are the other options that are configurable. Most of these can also be setup when configuring the Incoming WebHook on Slack, so by not setting them here, they default to the Slack settings. It's recommended to not set these options here (unless listed above) so that the default WebHook settings are applied.

channel

Specify a channel/user to post to in Slack instead of the WebHook's default

git config hooks.slack.channel '#channel'
    '#channel' - Post to channel
    '@username' - Direct message from @slackbot to user
    'groupname' - Post to group

username

Specify a username to post as. If not specified, the default name will be used that was created on Slack

git config hooks.slack.username 'Marty McFly'

icon-url

Specify an image to display in Slack instead of the default icon

git config hooks.slack.icon-url 'https://cdn4.iconfinder.com/data/icons/btf_LIN/LIN/256/delorean.png'

icon-emoji

Specify an emoji to display in Slack instead of the default icon

git config hooks.slack.icon-emoji ':ghost:'

repo-nice-name

Specify a repository nice-name that will be shown in messages

git config hooks.slack.repo-nice-name 'Our Awesome Project'

show-only-last-commit

Specify whether you want to show only the last commit (or all commits) when pushing multiple commits

git config hooks.slack.show-only-last-commit true

branch-regexp

Specify if you only want certain branches of the repository

git config hooks.slack.branch-regexp regexp