cli: changed help message (-h) to start with capital letter (#2591)

* cli: -h message now starts with capital letter
Fixes #1064

* Added explicit clarification for purposes of adding code

dvc/cli.py

@@ -144,6 +144,19 @@ def parse_args(argv=None):
         description=desc,
         parents=[parent_parser],
         formatter_class=argparse.RawTextHelpFormatter,
+        add_help=False,
+    )
+
+    # NOTE: We are doing this to capitalize help message.
+    # Unfortunately, there is no easier and clearer way to do it,
+    # as adding this argument in get_parent_parser() either in
+    # log_level_group or on parent_parser itself will cause unexpected error.
+    parser.add_argument(
+        "-h",
+        "--help",
+        action="help",
+        default=argparse.SUPPRESS,
+        help="Show this help message and exit.",
     )
 
     # NOTE: On some python versions action='version' prints to stderr