Add stub of command snapshot

In order to test the automatic release generation, some more reasons to increase the version number have to be found. Adding stubs of commands already planned to support is a good idea.

Thus, this change set provides a snapshot command and a test to ensure that this command is triggered if the program is called without arguments.

src/root_subvol_snapshot/cli.py

@@ -3,6 +3,7 @@
 
 This module provides the CLI to enter the program.
 """
+import sys
 import typing as t
 from pathlib import Path
 
@@ -11,6 +12,13 @@
 app = typer.Typer()
 
 
+def main() -> None:
+    if len(sys.argv) == 1:
+        snapshot()
+    else:
+        app()
+
+
 @app.command()
 def open(device: t.Annotated[t.Optional[Path], typer.Argument()] = None) -> None:
     typer.echo(f"Opening {device}...")
@@ -21,5 +29,10 @@ def close(device: t.Annotated[t.Optional[Path], typer.Argument()] = None) -> Non
     typer.echo(f"Closing {device}...")
 
 
+@app.command()
+def snapshot(device: t.Annotated[t.Optional[Path], typer.Argument()] = None) -> None:
+    typer.echo("Making a snapshot of the root subvolume...")
+
+
 if __name__ == "__main__":
-    app()
+    main()

tests/test_cli.py

@@ -1,4 +1,6 @@
-from root_subvol_snapshot.cli import app
+import sys
+
+from root_subvol_snapshot.cli import app, main
 from typer.testing import CliRunner
 
 runner = CliRunner()
@@ -10,6 +12,13 @@ def test_cli():
     assert "Show this message and exit." in result.output
 
 
+def test_cli_without_args_snapshots(capsys, monkeypatch):
+    monkeypatch.setattr(sys, "argv", [sys.argv[0]])
+    main()
+    captured = capsys.readouterr()
+    assert captured.out == "Making a snapshot of the root subvolume...\n"
+
+
 def test_open():
     result = runner.invoke(app, ["open"])
     assert result.exit_code == 0
@@ -32,3 +41,9 @@ def test_close_with_argument(tmp_path):
     result = runner.invoke(app, ["close", str(tmp_path)])
     assert result.exit_code == 0
     assert result.output.endswith(f"{tmp_path}...\n")
+
+
+def test_snapshot():
+    result = runner.invoke(app, ["snapshot"])
+    assert result.exit_code == 0
+    assert result.output.startswith("Making a snapshot of the root subvolume...")