Make min-similarity-lines == 0 stop similarity check

This makes it so that setting ``min-similarity-lines`` to zero exit the
similarity code checker with a successful exit.
This closes pylint-dev#4901

ChangeLog

@@ -63,6 +63,10 @@ Release date: TBA
 
   Closes #4907
 
+* Setting ``min-similarity-lines`` to 0 now makes the similarty checker stop checking for duplicate code
+
+  Closes #4901
+
 
 What's New in Pylint 2.10.3?
 ============================

doc/whatsnew/2.11.rst

@@ -69,3 +69,7 @@ Other Changes
 * Fix false positive ``superfluous-parens`` for tuples created with inner tuples
 
   Closes #4907
+
+* Setting ``min-similarity-lines`` to 0 now makes the similarty checker stop checking for duplicate code
+
+  Closes #4901

pylint/checkers/similar.py

@@ -919,6 +919,8 @@ def Run(argv=None):
             ignore_signatures = True
     if not args:
         usage(1)
+    if min_lines == 0:
+        sys.exit(0)
     sim = Similar(
         min_lines, ignore_comments, ignore_docstrings, ignore_imports, ignore_signatures
     )

tests/checkers/unittest_similar.py

@@ -502,3 +502,11 @@ def test_get_map_data() -> None:
         # There doesn't seem to be a faster way of doing this, yet.
         lines = (linespec.text for linespec in lineset_obj.stripped_lines)
         assert tuple(expected_lines) == tuple(lines)
+
+
+def test_set_duplicate_lines_to_zero() -> None:
+    output = StringIO()
+    with redirect_stdout(output), pytest.raises(SystemExit) as ex:
+        similar.Run(["--duplicates=0", SIMILAR1, SIMILAR2])
+    assert ex.value.code == 0
+    assert output.getvalue() == ""