First Git hook for Atlassian Bitbucket (formerly Atlassian Stash)

For my current project I’ve setup a full CI pipeline to automate the build process of the application (an EAR-file in this case) and deploy it to the test server. The build itself is a Maven build that runs all the tests and builds the EAR file. We are a number of people working on the application – some do frontend work (mainly JavaScript) and I do the backend. The Git repository we use is split into three branches as it concerns this project – one for backend (feature/eventboard_backend), one for frontend (feature/eventboard_frontend) and one that merges the two into the final result for building (feature/eventboard). So I was setting all this up – had the build script ready, the build server ready (Atlassian Bamboo), the deployment script working over SCP/SSH but I needed a nice way to automatically merge the two development branches into the main branch for the build.

The way I solved it was to write a Git post-receive hook on the Git server side (Atlassian Bitbucket). This post-receive hook detects a push to either of the two development branches and when it does merges the two into the main branch and pushes it branch back up. This push is in turn detected by Atlassian Bamboo that then kicks of the build and the deployment. So nice. Even though it took me a couple of hours to configure it has already saved so much time and all builds and deployments are consistant.

Today I extended the build script to monitor another branch so I now both deploy into our “bleeding edge” environment and our test environment.

The post-receive hook is written in bash and is as below. It took me a while to grok but a hook is simply a script that runs as the server OS user when ever something happens. The script is free to run as another user so my script runs as a special Git user so we can distinguish between which users does what. It also means that I could restrict access to feature/eventboard branch so it’s only writable by this build user.

The only caveat about this hook was that we are using Atlassian Bitbucket which apparently only accepts hooks written in Java. There is however a way to add bash-based hooks directly in the file system on the server under /<bitbucket-home>/shared/data/repositories/<repoid> where the repoid can be found in the repository settings on the Bitbucket server if logged in as admin.



while read oldrev newrev refname
        branch=$(git rev-parse --symbolic --abbrev-ref $refname)
        echo "Currently on branch '$branch'"
        if [ "$MONITOR_BRANCH1" == "$branch" ] || [ "$MONITOR_BRANCH2" == "$branch" ]; then
                echo "Detected commit on $MONITOR_BRANCH1 or $MONITOR_BRANCH2 - merging..."
                if [ ! -d "$WORKING_DIR" ]; then
                        mkdir -p $WORKING_DIR
                cd $WORKING_DIR
                unset GIT_DIR
                if [ ! -d "$CHECKOUT_NAME" ]; then
                        # repo doesn't exit - abort
                        echo "*** Required repo for post-receive hook not configured - exiting..."
                        cd $CHECKOUT_NAME
                        git reset --hard
                        git checkout $MERGE_INTO_BRANCH
                        git pull origin $MERGE_INTO_BRANCH
                git fetch origin $MONITOR_BRANCH1:$MONITOR_BRANCH1
                git fetch origin $MONITOR_BRANCH2:$MONITOR_BRANCH2
                git merge $MONITOR_BRANCH1 $MONITOR_BRANCH2 -m "Merged 
                          '$MONITOR_BRANCH1' and '$MONITOR_BRANCH2' into 
                git push origin $MERGE_INTO_BRANCH