code: private String getRevIDFromIfMatchHeader() {
          String ifMatch = getRequestHeaderValue("If-Match");
          if (ifMatch == null) {
              return null;
          }
          // Value of If-Match is an ETag, so have to trim the quotes around it:
          if (ifMatch.length() > 2 && ifMatch.startsWith("\"") && ifMatch.endsWith("\"")) {
              return ifMatch.substring(1, ifMatch.length() - 2);
          } else {
              return null;
          }
      }
docs: DOCUMENT REQUESTS: *