build.gradle

allprojects {
    ext.getLastGitTag = { ->
        try {
            def stdout = new ByteArrayOutputStream()
            exec {
                commandLine 'git', 'describe', '--abbrev=0', '--tags'
                standardOutput = stdout
            }
            return stdout.toString().trim()
        } catch (ignored) {
            return null
        }
    }

    ext.getLastGitTagWithNewCommit = { ->
        try {
            def stdout = new ByteArrayOutputStream()
            exec {
                commandLine 'git', 'describe', '--tags'
                standardOutput = stdout
            }
            return stdout.toString().trim()
        } catch (ignored) {
            return null
        }
    }

    ext.getVersionFromGitTag = { ->
        def pattern = ~/^v(\d{1,3})\.(\d{1,3})\.\d{1,4}$/
        def lastTag = getLastGitTag() ?: 'v0.0.0'
        if ((lastTag != null) && lastTag.matches(pattern) && (lastTag == getLastGitTagWithNewCommit())) {
            return lastTag.substring(1)
        }
        else {
            // See docs/releasing.md
            return "0.0.0-SNAPSHOT"
        }
    }
}