commands: add a shell command

This command spawns an interactive shell on your host but inside the
user and mount namespaces that pmbootstrap set up. It is mostly useful
for debugging issues with permissions, etc.

Signed-off-by: Casey Connolly <kcxt@postmarketos.org>

pmb/commands/shell.py

@@ -0,0 +1,14 @@
+# Copyright 2024 Caleb Connolly
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+from __future__ import annotations
+from pmb import commands
+import pmb.helpers.run
+
+
+class Shell(commands.Command):
+    def __init__(self) -> None:
+        pass
+
+    def run(self) -> None:
+        pmb.helpers.run.user(["sh", "-i"], output="tui", check=False)