Gradle Release Plugin

Gradle has a release plugin that mimics the Maven release plugin behaviour. i.e. you specify a snapshot version in your build and the plugin can update the version to a released version, commit and push that.

The plugin is not bundled / part of Gradle core, but available here:

https://github.com/researchgate/gradle-release

Configuration

To use it, set a snapshot version in your gradle.properties file, like:

version=1.1-SNAPSHOT

You build.gradle file config should be as follows:

plugins {
    id 'java'
    id 'net.researchgate.release' version '2.8.1'
    id 'maven-publish'
}

group 'com.something'

repositories {
    mavenLocal()
    mavenCentral()
    maven {
        url = uri('http://your-maven-repo:8080/repository/your-repo-url/')
    }
}

java {
    withSourcesJar()
}

publishing {
    publications {
        maven(MavenPublication) {
            from components.java
        }
    }

    repositories {
        // define our repo for publishing.
        // Note that you do not need to include maven local here to enable publishing of snapshots
        // to the local repo
        maven {
            name = "myRepo"
            def releasesRepoUrl = "http://myRepoURL:8080/repository/releases"
            def snapshotsRepoUrl = "http://myRepoURL:8080/repository/snapshots"
            url = version.endsWith('SNAPSHOT') ? snapshotsRepoUrl : releasesRepoUrl
            allowInsecureProtocol = true
            // credentials are not stored in the project, put them in gradle.properties on your build server
            credentials(PasswordCredentials)
        }
    }
}

// publish every build to local maven, to enable local testing
publishToMavenLocal.dependsOn(check)
build.dependsOn(publishToMavenLocal)
// publish release builds to remote repo
afterReleaseBuild.dependsOn publish

Diasabling git repo caching on Bamboo

If you use the Bamboo CI server, you can get this problem. By default, Bamboo will create a cached version of a git repository on a build agent. This seems to cause a release to fail as the cache appears to be created as a non-bare git repo. (Why!?) You will get an error like this:

build   12-Jul-2023 21:25:01    > Task :CPA-GJAP-JOB1:preTagCommit FAILED
build   12-Jul-2023 21:25:01    Running [git, push, --porcelain, origin, master] produced an error: [remote: error: refusing to update checked out branch: refs/heads/master       
build   12-Jul-2023 21:25:01    remote: error: By default, updating the current branch in a non-bare repository       
build   12-Jul-2023 21:25:01    remote: is denied, because it will make the index and work tree inconsistent       
build   12-Jul-2023 21:25:01    remote: with what you pushed, and will require 'git reset --hard' to match       
build   12-Jul-2023 21:25:01    remote: the work tree to HEAD.       
build   12-Jul-2023 21:25:01    remote:
build   12-Jul-2023 21:25:01    remote: You can set the 'receive.denyCurrentBranch' configuration variable       
build   12-Jul-2023 21:25:01    remote: to 'ignore' or 'warn' in the remote repository to allow pushing into       
build   12-Jul-2023 21:25:01    remote: its current branch; however, this is not recommended unless you       
build   12-Jul-2023 21:25:01    remote: arranged to update its work tree to match what you pushed in some       
build   12-Jul-2023 21:25:01    remote: other way.       
build   12-Jul-2023 21:25:01    remote:
build   12-Jul-2023 21:25:01    remote: To squelch this message and still keep the default behaviour, set       
build   12-Jul-2023 21:25:01    remote: 'receive.denyCurrentBranch' configuration variable to 'refuse'.       
build   12-Jul-2023 21:25:01    error: failed to push some refs to 'file:///opt/atlassian/bamboo_home/local-working-dir/_git-repositories-cache/75a29889fc2f629c383438079d8c939799ad3383']

You need to go into the Bamboo admin settings for that repository (not the build plan) and deselect “Enable repository caching on agents”.

Avoiding an infinite build loop with Bamboo

A second gotcha when using Bamboo! Bamboo is hard coded to understand and ignore Maven release plugin commits. This is not the case with the Gradle release plugin! Hence without additional configuration you will get an infinite loop. You can fix this by configuring the repository settings to ignore Gradle release plugin commits.

https://stackoverflow.com/questions/48692732/gradle-release-plugin-release-task-on-bamboo-cause-infinite-loop

You need to update the Bamboo admin settings for the repository, not to trigger builds when the commit message matches:

.*?Gradle Release Plugin.*?

initScmAdapter FAILED :Current Git branch is master not main

From v3 of the plugin onwards, the default git branch has changed from master to main. If you are still using master, you can configure this:

release {
    git {
        requireBranch.set('master')
    }
}

For other Gradle posts, see:
Dependencies and Configurations in Gradle
Using test fixtures in Gradle and Maven
Code coverage with Gradle and Jacoco