Add log level NONE and deprecate quiet

Fixes #154

src/con_duct/__main__.py

@@ -512,14 +512,14 @@ def from_argv(
             "-l",
             "--log_level",
             default=DEFAULT_LOG_LEVEL,
-            choices=("CRITICAL", "ERROR", "WARNING", "INFO", "DEBUG"),
-            help="Log level from duct operation.",
+            choices=("CRITICAL", "ERROR", "WARNING", "INFO", "DEBUG", "NONE"),
+            help="Log level from duct operation, use NONE to disable duct output to stderr.",
         )
         parser.add_argument(
             "-q",
             "--quiet",
             action="store_true",
-            help="Disable duct logging output (to stderr)",
+            help="[deprecated, use log level NONE] Disable duct logging output (to stderr)",
         )
         parser.add_argument(
             "--sample-interval",
@@ -737,9 +737,10 @@ def execute(args: Arguments) -> int:
 
     Returns exit code of the executed process.
     """
-    lgr.setLevel(args.log_level)
-    if args.quiet:
+    if args.log_level == "NONE" or args.quiet:
         lgr.disabled = True
+    else:
+        lgr.setLevel(args.log_level)
     log_paths = LogPaths.create(args.output_prefix, pid=os.getpid())
     log_paths.prepare_paths(args.clobber, args.capture_outputs)
     stdout, stderr = prepare_outputs(args.capture_outputs, args.outputs, log_paths)

test/test_execution.py

@@ -151,6 +151,17 @@ def test_outputs_none_quiet(
     # But nothing new to the log
     assert caplog.text == caplog_text1
 
+    # log_level NONE should have the same behavior as quiet
+    args.log_level = "NONE"
+    args.quiet = False
+    args.clobber = True  # to avoid the file already exists error
+    assert execute(args) == 0
+    r3 = capsys.readouterr()
+    # Still have all the outputs
+    assert r1 == r3
+    # But nothing new to the log
+    assert caplog.text == caplog_text1
+
 
 def test_exit_before_first_sample(temp_output_dir: str) -> None:
     args = Arguments.from_argv(