[lit] Refine adoption of argparse --version action

The real work for this was already done by serge-sans-paille [1].
Thanks for this!

[1] 1d4849379f71a0f5d73202a291c0b709f7cafbc5

utils/lit/lit/cl_arguments.py

@@ -5,18 +5,17 @@ import sys
 
 import lit.util
 
+
 def parse_args():
-    parser = argparse.ArgumentParser()
+    parser = argparse.ArgumentParser(prog='lit')
     parser.add_argument('test_paths',
             nargs='+',
             metavar="TEST_PATH",
             help='File or path to include in the test suite')
 
-    parser.add_argument("--version",
-            dest="show_version",
-            help="Show version and exit",
-            version="lit " + lit.__version__,
-            action="version")
+    parser.add_argument('--version',
+            action='version',
+            version='%(prog)s ' + lit.__version__)
 
     parser.add_argument("-j", "--threads", "--workers",
             dest="workers",
@@ -189,12 +188,15 @@ def parse_args():
 
     return opts
 
+
 def _positive_int(arg):
     return _int(arg, 'positive', lambda i: i > 0)
 
+
 def _non_negative_int(arg):
     return _int(arg, 'non-negative', lambda i: i >= 0)
 
+
 def _int(arg, kind, pred):
     desc = "requires {} integer, but found '{}'"
     try:
@@ -205,6 +207,7 @@ def _int(arg, kind, pred):
         raise _error(desc, kind, arg)
     return i
 
+
 def _case_insensitive_regex(arg):
     import re
     try:
@@ -212,6 +215,7 @@ def _case_insensitive_regex(arg):
     except re.error as reason:
         raise _error("invalid regular expression: '{}', {}", arg, reason)
 
+
 def _error(desc, *args):
     msg = desc.format(*args)
     return argparse.ArgumentTypeError(msg)

utils/lit/lit/main.py

@@ -20,7 +20,6 @@ import lit.util
 
 def main(builtin_params={}):
     opts = lit.cl_arguments.parse_args()
-
     params = create_params(builtin_params, opts.user_params)
     is_windows = platform.system() == 'Windows'
 

utils/lit/tests/usage.py

@@ -1,6 +1,7 @@
-# Basic sanity check that usage works.
+# Basic sanity check for `--help` and `--version` options.
 #
-# RUN: %{lit} --help > %t.out
-# RUN: FileCheck < %t.out %s
+# RUN: %{lit} --help         | FileCheck %s --check-prefix=HELP
+# RUN: %{lit} --version 2>&1 | FileCheck %s --check-prefix=VERSION
 #
-# CHECK: usage: lit.py [-h]
+# HELP: usage: lit [-h]
+# VERSION: lit {{[0-9]+\.[0-9]+\.[0-9]+[a-zA-Z0-9]*}}

utils/lit/tests/version.py

@@ -1,5 +0,0 @@
-# Basic sanity check that --version works.
-#
-# RUN: %{lit} --version 2>&1 | FileCheck %s
-#
-# CHECK: lit {{[0-9]+\.[0-9]+\.[0-9]+[a-zA-Z0-9]*}}