add a script for unpacking snapshot files

Summary:
Add a script for unpacking saved snapshot files.

This unpacks the tarball and then fixes up absolute paths inside the snapshot
so it will work at the unpacked location.  It also emits a small helper script
to make it easier to invoke eden for the snapshot.

Reviewed By: wez

Differential Revision: D12927842

fbshipit-source-id: f46c07a79894877842f2a78aa0924fd66e4c8969

eden/integration/snapshot/snapshot.py

@@ -493,7 +493,7 @@ def unpack_into(snapshot_path: Path, output_path: Path) -> BaseSnapshot:
     """
     # GNU tar is smart enough to automatically figure out the correct
     # decompression method.
-    untar_cmd = ["tar", "-xf", str(snapshot_path)]
+    untar_cmd = ["tar", "-xf", str(snapshot_path.absolute())]
     subprocess.check_call(untar_cmd, cwd=output_path)
 
     data_dir = output_path / "data"

eden/integration/snapshot/unpack_snapshot.py

@@ -0,0 +1,66 @@
+#!/usr/bin/env python3
+#
+# Copyright (c) 2016-present, Facebook, Inc.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree. An additional grant
+# of patent rights can be found in the PATENTS file in the same directory.
+
+import argparse
+import os
+from pathlib import Path
+
+from . import snapshot as snapshot_mod
+
+
+RUN_EDEN_SCRIPT = """\
+#!/bin/bash
+
+# Find the Eden binary to use.
+DEV_EDEN="buck-out/gen/eden/cli/eden.par"
+if [[ -n "$EDEN" ]]; then
+  # $EDEN is defined in the environment, so use that
+  :
+elif [[ -x "$DEV_EDEN" ]]; then
+  # We appear to be running from an fbcode directory with a built
+  # version of eden in buck-out.  Use it.
+  EDEN="$DEV_EDEN"
+else
+  # Find eden from $PATH
+  EDEN="eden"
+fi
+
+SNAPSHOT_PATH={snapshot_path}
+exec "$EDEN" \\
+  --etc-eden-dir "$SNAPSHOT_PATH/transient/etc_eden" \\
+  --config-dir "$SNAPSHOT_PATH/data/eden" \\
+  "$@"
+"""
+
+
+def main() -> None:
+    ap = argparse.ArgumentParser()
+    ap.add_argument("-o", "--output", required=True, help="The output directory path.")
+    ap.add_argument(
+        "--start", action="store_true", default=False, help="Also start EdenFS."
+    )
+    ap.add_argument("snapshot", help="The path of the snapshot file to unpack.")
+
+    args = ap.parse_args()
+
+    output_dir = Path(args.output)
+    input_path = Path(args.snapshot)
+    output_dir.mkdir()
+    snapshot_mod.unpack_into(input_path, output_dir)
+
+    # Write a small helper script that can be used to more easily invoke Eden in this
+    # repository.
+    run_eden_path = output_dir / "run_eden"
+    with run_eden_path.open("w") as f:
+        f.write(RUN_EDEN_SCRIPT.format(snapshot_path=output_dir))
+        os.fchmod(f.fileno(), 0o755)
+
+
+if __name__ == "__main__":
+    main()