code: protected String determineRootDir(String location) {
          int prefixEnd = location.indexOf(":") + 1;
          int rootDirEnd = location.length();
          while (rootDirEnd > prefixEnd && getPathMatcher().isPattern(location.substring(prefixEnd, rootDirEnd))) {
              rootDirEnd = location.lastIndexOf('/', rootDirEnd - 2) + 1;
          }
          if (rootDirEnd == 0) {
              rootDirEnd = prefixEnd;
          }
          return location.substring(0, rootDirEnd);
      }
docs: Determine the root directory for the given location.
  <p>Used for determining the starting point for file matching,
  resolving the root directory location to a <code>java.io.File</code>
  and passing it into <code>retrieveMatchingFiles</code>, with the
  remainder of the location as pattern.
  <p>Will return "/WEB-INF/" for the pattern "/WEB-INF/*.xml",
  for example.
  
  @param location the location to check
  @return the part of the location that denotes the root directory
  @see #retrieveMatchingFiles