Fix add_invertible_flag regression and ruff PIE810 violation

Restore the original add_invertible_flag logic where the argparse action
depends on the default value. The previous commit incorrectly simplified
this to always use store_true/store_false, which broke all 7 flags with
default=True (--no-namespace-packages, --no-warn-no-return,
--no-implicit-reexport, --no-color-output, --no-error-summary, etc).

The --pretty default is now controlled solely through Options.pretty=True
in options.py, keeping default=False in add_invertible_flag so the flag
semantics work correctly (--pretty -> store_true, --no-pretty -> store_false).

Also fix ruff PIE810 by merging startswith calls into a tuple.

Author: veeceey

mypy/main.py

@@ -524,9 +524,16 @@ def add_invertible_flag(
         if help is not argparse.SUPPRESS:
             help += f" (inverse: {inverse})"
 
-        arg = group.add_argument(flag, action="store_true", dest=dest, help=help)
+        arg = group.add_argument(
+            flag, action="store_false" if default else "store_true", dest=dest, help=help
+        )
         dest = arg.dest
-        group.add_argument(inverse, action="store_false", dest=dest, help=argparse.SUPPRESS)
+        group.add_argument(
+            inverse,
+            action="store_true" if default else "store_false",
+            dest=dest,
+            help=argparse.SUPPRESS,
+        )
         if strict_flag:
             assert dest is not None
             strict_flag_names.append(flag)
@@ -1000,7 +1007,7 @@ def add_invertible_flag(
     )
     add_invertible_flag(
         "--pretty",
-        default=True,
+        default=False,
         help="Use visually nicer output in error messages:"
         " Use soft word wrap, show source code snippets,"
         " and show error location markers",

mypy/test/testdaemon.py

@@ -86,7 +86,7 @@ def run_cmd(input: str) -> tuple[int, str]:
         elif input.startswith("mypy ") and " -- " in input:
             # For mypy commands, options come before --, so insert before --
             input = input.replace(" -- ", " --no-pretty -- ", 1)
-        elif input.startswith("dmypy run ") or input.startswith("dmypy start"):
+        elif input.startswith(("dmypy run ", "dmypy start")):
             # dmypy commands without -- need the separator added
             input += " -- --no-pretty"
         elif input.startswith("mypy "):