Git pre-hook: Setup pre-commit hook for Gradle project example

Introduction

There are various Git pre-hooks that are quite helpful for several essential tasks we want to execute before commit or push or rebase etc. Basically, there are various use cases, like running linting before you commit or running unit tests before push or commit.

Whenever a Git repository is initialized, Git creates sample hooks inside .git/hooks directory in the project directory. E.g. .git/hooks/pre-commit.sample

Getting Started

Below are steps on how to configure pre-hook for a Gradle project:

1. Create a pre-hook script

Let's create pre-commit file inside a new scripts directory, and we want to run unit tests before code commit.

#!/bin/sh

echo "*****Running unit tests******"

stash_commit="$(git stash create)"
git reset —-hard

./gradlew test

status=$?

if [[ -n "${stash_commit}" ]]
then git stash apply "${stash_commit}"
fi

echo "*****Done with unit tests******"

exit $status

Above command stash the working directory changes before running the unit tests, and unstash back. This makes sure, we're running unit tests only in the clean working directory. (as this is been configured for pre-commit, changes must have been staged, make sense?😀)

2. Create Gradle Task

Next, create a Gradle task in the build.gradle file to install the pre-commit script. Why do we need it? because, we want this to run on all developers' machine, not just on our machine, we all love consistency and wants to put the constraints.

task installLocalGitHook(type: Copy){
from new File(rootProject.rootDir, 'scripts/pre-commit')
into { new File(rootProject.rootDir, '.git/hooks')}
fileMode 0775
}

build.dependsOn installLocalGitHook

Here pre-commit file was created inside project root directory i.e. scripts

Above Gradle task will run whenever someone takes the build and assuming that developer who is making changes will run the Gradle build task at least once and I hope I'm right😉.

Once pre-commit script is copied to .git/hooks/ directory, we're all set. We can verify its content as below:

cat .git/hooks/pre-commit

Now, next time whenever someone will run git commit, it will first run the ./gradlew test task.

E.g.

ak@--mac git-pre-commit % git commit -am "update"

-- Output

*****Running unit tests******

BUILD SUCCESSFUL in 1s
4 actionable tasks: 4 up-to-date
[main ed41136] update
 1 file changed, 13 insertions(+), 1 deletion(-)

Final Notes

• The way ./gradlew test is configured, in the same way, any other tasks can be executed. And of course for other tasks stash and unstash won't be compulsory.
• And similarly other pre-hooks can be configured

Sample Code

Here is the GitHub repo with an example.

My other Blogs:

• Avoid Spring RestTemplate Default Implementation to Prevent Performance Impact
• Post on how to setup pre-hook for an NPM project
• Team Agreement in Software Engineering
• Containers Vs Virtual Machines, which is better and why?

If you have reached here, then I did a satisfactory effort to keep you reading. Please be kind to leave any comments or ask for any corrections. Happy Coding!