docs: function readPackedRef(gitFolder, refName) {
  	var packedRefs, i, each, match
  
  	try {
  		packedRefs = fs.readFileSync(path.join(gitFolder, 'packed-refs'), 'utf8').split(/\r?\n/)
  	} catch (e) {
  		return ''
  	}
  
  	for (i = 0; i < packedRefs.length; i++) {
  		each = packedRefs[i].trim()
  
  		// Look for lines like:
  		// 1d6f5f98a254578e19b5eb163077170d45448c26 refs/heads/master
  		match = each.match(/^(.{40}) (.*)$/)
  		if (match && match[2] === refName && isSHA1(match[1])) {
  			return match[1]
  		}
  	}
  	return ''
  }