Add edenfs specific file watcher tests

Summary:
# Context

We are introducing EdenFS notifications to support scalable and ergonomic file system notifications for EdenFS mounts.

# This Diff

* Adds additional edenfs specific file watcher tests.
* We would like to test remount/restart, but that leaves the test in bad state when running on an eden mount.

# Next Steps

* Fix bug in EdenFS that causes `to` and `from` to be switched in commit transitions.
* After fix deployed - remove work around in edenfs file watcher.

Differential Revision: D67614187

fbshipit-source-id: a51b5c5ec630670489e83e1c4af33ca05e4d69ca

tests/core/io/test_edenfs.py

@@ -7,7 +7,12 @@
 
 # pyre-strict
 
-from buck2.tests.core.common.io.file_watcher import FileWatcherProvider
+import subprocess
+
+from buck2.tests.core.common.io.file_watcher import (
+    FileWatcherProvider,
+    get_file_watcher_events,
+)
 from buck2.tests.core.common.io.file_watcher_dir_tests import (
     run_create_directory_test,
     run_remove_directory_test,
@@ -26,7 +31,10 @@
     run_rebase_wtih_mergebase_test,
     run_restack_wtih_mergebase_test,
 )
-from buck2.tests.core.common.io.file_watcher_tests import FileSystemType
+from buck2.tests.core.common.io.file_watcher_tests import (
+    FileSystemType,
+    setup_file_watcher_test,
+)
 
 from buck2.tests.e2e_util.api.buck import Buck
 from buck2.tests.e2e_util.buck_workspace import buck_test
@@ -115,3 +123,12 @@ async def test_edenfs_restack_with_mergebase(buck: Buck) -> None:
     await run_restack_wtih_mergebase_test(
         buck, FileSystemType.EDEN_FS, FileWatcherProvider.EDEN_FS
     )
+
+
+@buck_test(setup_eden=True)
+async def test_edenfs_truncate_journal(buck: Buck) -> None:
+    await setup_file_watcher_test(buck)
+    subprocess.run(["edenfsctl", "debug", "flush_journal"], cwd=buck.cwd)
+
+    is_fresh_instance, _ = await get_file_watcher_events(buck)
+    assert is_fresh_instance