Fix formatting of description of systemd command

When running "podman-compose", the list of commands gets displayed.
The systemd command is an outlier, showing multiple lines, IMO
unintended at this location.

This change moves the longer command description to its proper place,
that is, it gets shown when "podman-compose systemd --help" is
executed.

Signed-off-by: Cleber Rosa <[email protected]>

Author: clebergnu

podman_compose.py

@@ -1606,7 +1606,7 @@ def _parse_args(self):
         _ = subparsers.add_parser("help", help="show help")
         for cmd_name, cmd in self.commands.items():
             subparser = subparsers.add_parser(
-                cmd_name, help=cmd.desc
+                cmd_name, help=cmd.help, description=cmd.desc
             )  # pylint: disable=protected-access
             for cmd_parser in cmd._parse_args:  # pylint: disable=protected-access
                 cmd_parser(subparser)
@@ -1713,7 +1713,13 @@ def wrapped(*args, **kw):
 
         wrapped._compose = self.compose
         # Trim extra indentation at start of multiline docstrings.
-        wrapped.desc = self.cmd_desc or re.sub(r"^\s+", "", func.__doc__)
+        help_desc = self.cmd_desc or re.sub(r"^\s+", "", func.__doc__)
+        if "\n" in help_desc:
+            wrapped.help, wrapped.desc = help_desc.split("\n", 1)
+        else:
+            wrapped.help = help_desc
+            wrapped.desc = None
+
         wrapped._parse_args = []
         self.compose.commands[self.cmd_name] = wrapped
         return wrapped