Improve help text of user key of provision plugins

tmt/guest/__init__.py

@@ -2811,7 +2811,11 @@ class GuestSshData(GuestData):
         default=DEFAULT_USER,
         option=('-u', '--user'),
         metavar='NAME',
-        help='A username to use for all guest operations.',
+        help="""
+             Username to use when connecting to the guest via SSH. Unless
+             ``become`` is used, tests and other user-provided commands
+             will be invoked under this user account.
+             """,
     )
     key: list[Path] = field(
         default_factory=list,

tmt/steps/provision/podman.py

@@ -52,7 +52,13 @@ class PodmanGuestData(tmt.guest.GuestData):
         default=DEFAULT_USER,
         option=('-u', '--user'),
         metavar='USERNAME',
-        help='Username to use for all guest operations.',
+        help="""
+             Username to pass to ``podman run`` command when starting the
+             container representing the guest. It will override ``USER``
+             directive from the image. Unless ``become`` is used, tests
+             and other user-provided commands will be invoked under this
+             user account.
+             """,
     )
     force_pull: bool = field(
         default=False,