get versionCode from manifest

build.gradle

def getVersionCodeFromManifest() {
    def manifestContent = file(android.sourceSets.main.manifest.srcFile).getText()
    def matcher = (~"versionCode=\"(\\d+)\"").matcher(manifestContent)
    matcher.find()
    return Integer.parseInt(matcher.group(1))
}

def getVersionCodeFromManifestLong() {
    def manifestFile = android.sourceSets.main.manifest.srcFile
    def xpath = XPathFactory.newInstance().newXPath()

    xpath.setNamespaceContext(new NamespaceContext() {
        final String nsPrefix = "android";
        final String nsURI = "http://schemas.android.com/apk/res/android"

        public String getNamespaceURI(String prefix) {
            if (nsPrefix.equals(prefix)) {
                return nsURI;
            }
            return XMLConstants.NULL_NS_URI;
        }

        public String getPrefix(String namespaceURI) {
            if (nsURI.equals(namespaceURI)) {
                return nsPrefix;
            }
            return null;
        }

        public Iterator getPrefixes(String namespaceURI) {
            if (nsURI.equals(namespaceURI)) {
                ArrayList<String> list = new ArrayList<String>();
                list.add(nsPrefix);
                return list.iterator();
            }
            return null;
        }
    })
    return Integer.parseInt(xpath.evaluate("/manifest/@android:versionCode",
            new InputSource(new FileInputStream(manifestFile))))
}