cli: add -i option to enter interactive loop after command line argum…

…ents

src/dtsh/cli.py

@@ -65,12 +65,19 @@ def __init__(self) -> None:
             metavar="FILE",
         )
 
-        self._parser.add_argument(
+        grp_session_ctrl = self._parser.add_argument_group("session control")
+        grp_session_ctrl.add_argument(
             "-c",
             help="execute commands from CMD instead of the standard input",
             action="append",
             metavar="CMD",
         )
+        grp_session_ctrl.add_argument(
+            "-i",
+            "--interactive",
+            help="enter interactive loop after command line arguments",
+            action="store_true",
+        )
 
         self._argv = self._parser.parse_args()
 
@@ -112,6 +119,14 @@ def cli_cmds(self) -> Optional[List[str]]:
             return cast(List[str], self._argv.c)
         return None
 
+    @property
+    def interactive(self) -> bool:
+        """Is the interactive loop requested?"""
+        if not self._argv.c:
+            # no commands, must be interactive
+            return True
+        return self._argv.interactive
+
 
 def _load_preference_file(path: str) -> None:
     try:
@@ -159,7 +174,7 @@ def run() -> None:
         sys.exit(-22)
 
     if session:
-        session.run(argv.cli_cmds)
+        session.run(argv.cli_cmds, argv.interactive)
 
 
 if __name__ == "__main__":

src/dtsh/session.py

@@ -128,7 +128,7 @@ def __init__(
             self._autocomp.display,
         )
 
-    def run(self, cli_cmds: Optional[List[str]]) -> None:  # pylint: disable=too-many-branches
+    def run(self, cli_cmds: Optional[List[str]], interactive: bool) -> None:  # pylint: disable=too-many-branches
         """Enter command processing loop.
 
         This will:
@@ -146,12 +146,13 @@ def run(self, cli_cmds: Optional[List[str]]) -> None:  # pylint: disable=too-man
 
         Args:
             cli_cmds: List of command lines to execute in batch mode.
+            interactive: True if the session will enter an interactive loop.
         """
         # closing() the session when the pager is active breaks the TTY.
         # As a work-around, we ignore SIGINT.
         signal.signal(signal.SIGINT, self._sig_handler)
 
-        if not cli_cmds:
+        if interactive:
             self._vt.clear()
             self.preamble_hook()
 
@@ -177,8 +178,14 @@ def run(self, cli_cmds: Optional[List[str]]) -> None:  # pylint: disable=too-man
                 # Exit DTSh on EOF.
                 self.close()
             except IndexError:
-                # Exit DTSh on end of command line args.
-                self.close(interactive=False)
+                if not interactive:
+                    # Exit DTSh on end of command line args.
+                    self.close(interactive=False)
+                else:
+                    # Forget about CLI commands and continue with
+                    # an interactive session.
+                    cli_cmds = None
+                    continue
 
             if cmdline:
                 if cmdline.strip() in ["q", "quit", "exit"]: