Dynamic versions for gradle, git and Java development

dynamicVersion.gradle

/*
 * This work is licensed under the Creative Commons Attribution 3.0 Unported License.
 *
 * To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0/
 * or send a letter to Creative Commons, 444 Castro Street, Suite 900, Mountain View, California, 94041, USA.
 */
 
/* Define your version here. */
version = new Version(project: project, major: 1, minor: 0).toString()
 
/*
 * Print the version.
 */
task printVersion {
	doFirst {
		println "$project.version"
	}
}

/**
 * <p>
 * Implementation of a dynamic version for gradle builds that
 * includes a git commit hash.
 * </p>
 * <p>
 * Based on <a href="https://gist.github.com/jabbrwcky/3999533">dyamicVersion.gradle</a> by <a href="https://github.com/jabbrwcky">Jens Hausherr</a>.
 * </p>
 *
 * @author David Bull <a href="https://github.com/ukdave">ukdave@github</a>
 */
class Version {
	/* Reference to current gradle project */
	Project project
	
	/* Version number components, major and minor are required, the rest is optional. */
	int major, minor, revision, patch
	 
	/**
	 * Wrapper for git execution.
	 *
	 * @param gitArgs list of arguments to the git executable
	 * @return output of command
	 */
	def git(List gitArgs) {
		def stdout = new ByteArrayOutputStream()

		project.exec {
			executable = 'git'
			args = gitArgs
			standardOutput = stdout
		}
	 
		return stdout
	}

	/**
	 * Returns the version string.
	 *
	 * @return version string
	 */
	String toString() {
		def version = "$major.$minor"

		// Resolves the git revision
		def output = git([ "rev-parse", "--short", "HEAD" ])

		def commitMatcher = output =~ /([0-9a-f]{7})/
		def commit = commitMatcher[0][1]
		
		if (commit) {
			version += "-$commit"
		}
		 
		return version
	}
}