githead

/**
 * #388 Manifest header to get GIT head Get the head commit number. Look
 * for a .git/HEAD file, going up in the file hierarchy. Then get this file,
 * and resolve any symbolic reference.
 *
 * @throws IOException
 */
static Pattern	GITREF	= Pattern.compile("ref:\\s*(refs/(heads|tags|remotes)/([^\\s]+))\\s*");

static String	_githeadHelp	= "${githead}, provide the SHA for the current git head";

public String _githead(String[] args) throws IOException {
	Macro.verifyCommand(args, _githeadHelp, null, 1, 1);

	//
	// Locate the .git directory
	//

	File rover = getBase();
	while (rover !=null && rover.isDirectory()) {
		File headFile = IO.getFile(rover, ".git/HEAD");
		if (headFile.isFile()) {
			//
			// The head is either a symref (ref: refs/(heads|tags|remotes)/<name>)
			//
			String head = IO.collect(headFile).trim();
			if (!Hex.isHex(head)) {
				//
				// Should be a symref
				//
				Matcher m = GITREF.matcher(head);
				if (m.matches()) {

					// so the commit is in the following path

					head = IO.collect(IO.getFile(rover, ".git/" + m.group(1)));
				}
				else {
					error("Git repo seems corrupt. It exists, find the HEAD but the content is neither hex nor a sym-ref: %s",
							head);
				}
			}
			return head.trim().toUpperCase();
		}
		rover = rover.getParentFile();
	}
	// Cannot find git directory
	return "";
}