tft: rename "main.py" to "tft.py"

We have multple python scripts that are directly executable (i.e. they
have a main() function).

When running the test, it's not obvious why this program is called
`main.py`. Rename it to `tft.py`. You should now run `tft.py`.

Add a symlink `main.py` that points to the new script. This is for
backward compatibility, so that the various callers don't need to update
their code (yet).

README.md

@@ -113,7 +113,7 @@ tool will try to autopopulate resource_name based on the secondary+network_nad p
 Simply run the python application as so:
 
 ```
-python main.py config.yaml
+./tft.py config.yaml
 ```
 
 ## Environment variables

main.py

@@ -0,0 +1 @@
+tft.py

tft.py

@@ -0,0 +1,74 @@
+#!/usr/bin/env python3
+
+import argparse
+
+from pathlib import Path
+
+from ktoolbox import common
+
+from testConfig import TestConfig
+from testConfig import ConfigDescriptor
+from trafficFlowTests import TrafficFlowTests
+
+
+def parse_args() -> argparse.Namespace:
+
+    parser = argparse.ArgumentParser(
+        description="test Traffic Flows in an OVN-Kubernetes cluster."
+    )
+    parser.add_argument(
+        "config",
+        metavar="config",
+        type=str,
+        help="YAML file with test configuration (see config.yaml)",
+    )
+    parser.add_argument(
+        "evaluator_config",
+        nargs="?",
+        metavar="evaluator_config",
+        type=str,
+        help="YAML file with configuration for scoring test results (see eval-config.yaml). "
+        "This parameter is optional. If provided, this effectively runs "
+        "./evaluator.py ${evaluator_config} ${test_result} ${evaluator_result}` on "
+        "the result file. You can run this step separately.",
+    )
+    parser.add_argument(
+        "-o",
+        "--output-base",
+        type=str,
+        default=None,
+        help="The base name for the result files. If specified, the result will be "
+        'written to "${output_base}$(printf \'%%03d\' "$number").json" where ${number} is the '
+        "zero-based index of the test. This can include the directory name and is relative to "
+        'the current directory. If unspecified, the files are written to "${logs}/${timestamp}.json" '
+        'where "${logs}" can be specified in the config file (and defaults to "./ft-logs/").',
+    )
+
+    common.log_argparse_add_argument_verbosity(parser)
+
+    args = parser.parse_args()
+
+    common.log_config_logger(args.verbosity, "tft", "ktoolbox")
+
+    if not Path(args.config).exists():
+        raise ValueError("Must provide a valid config.yaml file (see config.yaml)")
+
+    return args
+
+
+def main() -> None:
+    args = parse_args()
+
+    tc = TestConfig(
+        config_path=args.config,
+        evaluator_config=args.evaluator_config,
+        output_base=args.output_base,
+    )
+    tft = TrafficFlowTests()
+
+    for cfg_descr in ConfigDescriptor(tc).describe_all_tft():
+        tft.test_run(cfg_descr)
+
+
+if __name__ == "__main__":
+    main()