Git hooks example

Git hooks are scripts that perform automated actions when a specific action is performed in GitKraken Client or the command line. The git hook name usually indicates the hook’s trigger (e.g. pre-commit).

Git hooks live under the .git folder of your repo in a directory called hooks. The path to the hooks will look similar to repo/.git/hooks.

---

Tools needed

• GitKraken Client
• Text Editor – I will be using Visual Studio Code
• Terminal – I will be using iTerm2

Hook Purpose

In this example, we’ll create a pre-commit hook. This hook validates the git config’s global user email and checks whether a gpg key exists. The hook is useful so that the commits contain the correct committer email address and also to ensure the commits are signed.

Creating the git hook

Step 1

First navigate to the hooks directory for the target repo. Open a Visual Studio Code window and navigate to repo      .git       hooks. From here, add a new file to the .git/hooks directory called pre-commit.

Step 2

Now that we have our pre-commit file, we need to make it executable. To do this we will need the command line.

Open a terminal window by using option + T in GitKraken Client. Once the terminal windows is open, change directory to .git/hooks.

Then use the command chmod +x pre-commit to make the pre-commit file executable.

Step 3

Now we create our script using bash. In order for the script to run, we first need to specify our shell. Do this by using #!/bin/bash at the beginning of your script for bash or #!/bin/sh if using the sh shell. Any script that exits with anything other than exit code 0 is considered a fail.

This pre-commit hook watches for incorrect commit authors and unsigned commits using the script below.

Script variables:
PWD – Print working directory
globalEmail – Get email in global git config
signingKey – Get key in global git config
workEmail – This is your target email address. The email needed to commit successfully.

Now to explore the conditions we have set for our script. First we validate that the working directory contains demo and that the global git config user.email matches with our workEmail. If it fails we will see:

        echo "Commit email and global git config email differ"
        echo "Global commit email: "$globalEmail""
        echo "Committing email expected: $workEmail"
        exit 1

If the condition is met we move on to the next condition. If the global user.signingKey is empty we display:

        echo "No signing key found. Check global gitconfig"
        exit 1

If the condition is successful the script will run and the commit will be made.

Full Script

#!/bin/bash

PWD=`pwd`
globalEmail=`git config --global --get user.email`
signingKey=`git config --global --get user.signingkey`
workEmail="[email protected]"

if [[ $PWD != "*demo*" && $globalEmail != $workEmail ]];
then
        echo "Commit email and global git config email differ"
        echo "Global commit email: "$globalEmail""
        echo "Committing email expected: $workEmail"
        exit 1
elif [[ $signingKey -eq "" ]];
then
        echo "No signing key found. Check global gitconfig"
        exit 1
else
        echo ""
        exit 0
fi

Git hook in action