test(e2e): add docker-based end-to-end coverage for --backups-root and --force-keep

- Run E2E suite via unittest discovery inside the container
- Add E2E test for --id mode with real filesystem + fake dirval
- Add E2E test for --all + --force-keep to ensure latest backups are skipped

https://chatgpt.com/share/6954d89e-bf08-800f-be4a-5d237d190ddd

tests/e2e/test_e2e_force_keep.py

@@ -0,0 +1,163 @@
+#!/usr/bin/env python3
+import os
+import subprocess
+import tempfile
+import unittest
+from pathlib import Path
+
+
+FAKE_TIMEOUT_SLEEP = 0.3
+SHORT_TIMEOUT = "0.1"
+
+FAKE_DIRVAL = f"""#!/usr/bin/env python3
+import sys, time, argparse, pathlib
+
+def main():
+    p = argparse.ArgumentParser()
+    p.add_argument("path")
+    p.add_argument("--validate", action="store_true")
+    args = p.parse_args()
+
+    d = pathlib.Path(args.path)
+    name = d.name.lower()
+
+    if "timeout" in name:
+        time.sleep({FAKE_TIMEOUT_SLEEP})
+        print("Simulated long run...")
+        return 0
+
+    if (d / "VALID").exists():
+        print("ok")
+        return 0
+
+    print("failed")
+    return 1
+
+if __name__ == "__main__":
+    sys.exit(main())
+"""
+
+
+class CleanbackE2EForceKeepTests(unittest.TestCase):
+    """
+    E2E test that validates --force-keep in --all mode.
+    It creates two backup folders directly under /Backups so --all can find them:
+      /Backups/<prefix>-01/backup-docker-to-local/{good,bad}
+      /Backups/<prefix>-02/backup-docker-to-local/{good,bad}
+    With --force-keep 1, the last (sorted) backup folder (<prefix>-02) is skipped.
+    """
+
+    def setUp(self):
+        self.backups_root = Path("/Backups")
+        self.backups_root.mkdir(parents=True, exist_ok=True)
+
+        # Unique prefix to avoid collisions across runs
+        self.prefix = f"E2EKEEP-{os.getpid()}"
+
+        # Create fake `dirval` executable on disk (real file, real chmod)
+        self.bin_dir = Path(tempfile.mkdtemp(prefix="cleanback-bin-"))
+        self.dirval = self.bin_dir / "dirval"
+        self.dirval.write_text(FAKE_DIRVAL, encoding="utf-8")
+        self.dirval.chmod(0o755)
+
+        # Two backup folders directly under /Backups (so --all can discover them)
+        self.b1 = self.backups_root / f"{self.prefix}-01" / "backup-docker-to-local"
+        self.b2 = self.backups_root / f"{self.prefix}-02" / "backup-docker-to-local"
+        self.b1.mkdir(parents=True, exist_ok=True)
+        self.b2.mkdir(parents=True, exist_ok=True)
+
+        # Within each: good + bad
+        self.b1_good = self.b1 / "good"
+        self.b1_bad = self.b1 / "bad"
+        self.b2_good = self.b2 / "good"
+        self.b2_bad = self.b2 / "bad"
+
+        for p in (self.b1_good, self.b1_bad, self.b2_good, self.b2_bad):
+            p.mkdir(parents=True, exist_ok=True)
+
+        # Mark goods as valid
+        (self.b1_good / "VALID").write_text("1", encoding="utf-8")
+        (self.b2_good / "VALID").write_text("1", encoding="utf-8")
+
+        # Convenience for teardown
+        self.created_roots = [
+            self.backups_root / f"{self.prefix}-01",
+            self.backups_root / f"{self.prefix}-02",
+        ]
+
+    def tearDown(self):
+        # Cleanup created backup folders
+        for root in self.created_roots:
+            try:
+                if root.exists():
+                    for p in sorted(root.rglob("*"), reverse=True):
+                        try:
+                            if p.is_dir():
+                                p.rmdir()
+                            else:
+                                p.unlink()
+                        except Exception:
+                            pass
+                    try:
+                        root.rmdir()
+                    except Exception:
+                        pass
+            except Exception:
+                pass
+
+        # Cleanup temp bin dir
+        try:
+            if self.bin_dir.exists():
+                for p in sorted(self.bin_dir.rglob("*"), reverse=True):
+                    try:
+                        if p.is_dir():
+                            p.rmdir()
+                        else:
+                            p.unlink()
+                    except Exception:
+                        pass
+                try:
+                    self.bin_dir.rmdir()
+                except Exception:
+                    pass
+        except Exception:
+            pass
+
+    def test_all_mode_force_keep_skips_last_backup_folder(self):
+        env = os.environ.copy()
+        env["PATH"] = f"{self.bin_dir}:{env.get('PATH', '')}"
+
+        cmd = [
+            "python",
+            "-m",
+            "cleanback",
+            "--backups-root",
+            "/Backups",
+            "--all",
+            "--force-keep",
+            "1",
+            "--dirval-cmd",
+            "dirval",
+            "--workers",
+            "4",
+            "--timeout",
+            SHORT_TIMEOUT,
+            "--yes",
+        ]
+        proc = subprocess.run(cmd, text=True, capture_output=True, env=env)
+
+        self.assertEqual(proc.returncode, 0, msg=proc.stderr or proc.stdout)
+
+        # First backup folder (<prefix>-01) should be processed: bad removed, good kept
+        self.assertTrue(self.b1_good.exists(), "b1 good should remain")
+        self.assertFalse(self.b1_bad.exists(), "b1 bad should be deleted")
+
+        # Last backup folder (<prefix>-02) should be skipped entirely: both remain
+        self.assertTrue(self.b2_good.exists(), "b2 good should remain (skipped)")
+        self.assertTrue(self.b2_bad.exists(), "b2 bad should remain (skipped)")
+
+        self.assertIn("Summary:", proc.stdout)
+
+
+if __name__ == "__main__":
+    unittest.main(verbosity=2)