Add --fork-list arg to testgen to filter forks

tests/core/pyspec/eth2spec/gen_helpers/gen_base/gen_runner.py

@@ -171,7 +171,6 @@ def run_generator(generator_name, test_providers: Iterable[TestProvider]):
         help="if set re-generate and overwrite test files if they already exist",
     )
     parser.add_argument(
-        "-l",
         "--preset-list",
         dest="preset_list",
         nargs='*',
@@ -179,6 +178,14 @@ def run_generator(generator_name, test_providers: Iterable[TestProvider]):
         required=False,
         help="specify presets to run with. Allows all if no preset names are specified.",
     )
+    parser.add_argument(
+        "--fork-list",
+        dest="fork_list",
+        nargs='*',
+        type=str,
+        required=False,
+        help="specify forks to run with. Allows all if no fork names are specified.",
+    )
     parser.add_argument(
         "-c",
         "--collect-only",
@@ -199,6 +206,7 @@ def run_generator(generator_name, test_providers: Iterable[TestProvider]):
     print(f"Generating tests into {output_dir}")
     print(f'Error log file: {log_file}')
 
+    # preset_list arg
     presets = args.preset_list
     if presets is None:
         presets = []
@@ -206,6 +214,14 @@ def run_generator(generator_name, test_providers: Iterable[TestProvider]):
     if len(presets) != 0:
         print(f"Filtering test-generator runs to only include presets: {', '.join(presets)}")
 
+    # fork_list arg
+    forks = args.fork_list
+    if forks is None:
+        forks = []
+
+    if len(presets) != 0:
+        print(f"Filtering test-generator runs to only include forks: {', '.join(forks)}")
+
     collect_only = args.collect_only
 
     diagnostics_obj = Diagnostics()
@@ -224,6 +240,10 @@ def run_generator(generator_name, test_providers: Iterable[TestProvider]):
             if len(presets) != 0 and test_case.preset_name not in presets:
                 continue
 
+            # If fork list is assigned, filter by forks.
+            if len(forks) != 0 and test_case.fork_name not in forks:
+                continue
+
             case_dir = get_test_case_dir(test_case, output_dir)
             print(f"Collected test at: {case_dir}")
             diagnostics_obj.collected_test_count += 1