Fix samples/tags.cpp to call ExifTags::taglist() (https://github.com/Exiv2/exiv2/issues/465)

samples/taglist.cpp

@@ -49,15 +49,12 @@ int main(int argc, char* argv[])
                     }
                    */
                     const GroupInfo* groupList = ExifTags::groupList();
-                    int count = 0;
                     if (groupList) {
-                        while (groupList->tagList_ && count < 10000) {
-                            count++;
+                        while (groupList->tagList_) {
                             std::cout << groupList->groupName_ << std::endl;
                             groupList++;
                         }
                     }
-                    std::cout << "Groups = " << count << std::endl;
                     break;
                 }
 
@@ -89,29 +86,36 @@ int main(int argc, char* argv[])
                 break;
 
             case 3: {
-                rc = 1;  // assume unhappy ending!
                 std::string item(argv[1]);
                 std::string name(argv[2]);
+                rc = 1;  // assume unhappy ending!
 
                 if (item == "--group") {
+                    if ( ExifTags::isExifGroup(name) ) {
+                        ExifTags::taglist(std::cout,name);
+                        rc = 0;  // result is good
+                    } else {
+                        std::cerr << "warning:"
+                                  << name
+                                  << " is not a valid Exif group name "
+                                  << std::endl
+                                  ;
                         const GroupInfo* groupList = ExifTags::groupList();
                         if (groupList) {
-                        while (groupList->tagList_) {
-                            int count = 0;
+                            while (rc && groupList->tagList_) {
                                 if (name == groupList->groupName_) {
                                     const Exiv2::TagInfo* tagInfo = groupList->tagList_();
                                     while (tagInfo->tag_ != 0xFFFF) {
                                         std::cout << tagInfo->name_ << std::endl;
                                         tagInfo++;
-                                    count++;
                                     }
                                     rc = 0;  // result is good
-                                std::cout << "Tags = " << count << std::endl;
                                 }
                                 groupList++;
                             }
                         }
                     }
+                }
             } break;
 
             default: