Add support for optional argument in -i option for in-place editing

src/Options.cpp

@@ -185,6 +185,18 @@ ParseResult OptionParser::parse(int argc, char **argv) const {
           case 'r':
             result.options.extendedRegex = true;
             break;
+          case 'i':
+            // GNU sed accepts -i as an option with an optional argument.  When
+            // it appears inside a short-option cluster, any remaining bytes in
+            // that argv word are the backup suffix, e.g. -nri~ == -n -r -i~.
+            // If there are no remaining bytes, it is plain in-place editing and
+            // does not consume the next argv entry.
+            result.options.inPlace = true;
+            if (j + 1 < arg.size()) {
+              result.options.inPlaceSuffix = arg.substr(j + 1);
+              j = arg.size();
+            }
+            break;
           case 'z':
             result.options.nullData = true;
             break;