f Always use MoveFileExW

As we'll account for potentially open files via unique temp file names
and locking, we should be good to always use `MoveFileExW`, which also
gives us `fsync`-like properties via `MOVEFILE_WRITE_THROUGH`:

"The function does not return until the file is actually moved on the disk.
Setting this value guarantees that a move performed as a copy and delete
operation is flushed to disk before the function returns. The flush
occurs at the end of the copy operation."

Author: tnull

lightning-persister/src/fs_store.rs

@@ -137,27 +137,14 @@ impl KVStore for FilesystemStore {
 
 		#[cfg(target_os = "windows")]
 		{
-			if dest_file_path.exists() {
-				call!(unsafe {
-					windows_sys::Win32::Storage::FileSystem::ReplaceFileW(
-						path_to_windows_str(dest_file_path).as_ptr(),
-						path_to_windows_str(tmp_file_path).as_ptr(),
-						std::ptr::null(),
-						windows_sys::Win32::Storage::FileSystem::REPLACEFILE_IGNORE_MERGE_ERRORS,
-						std::ptr::null_mut() as *const core::ffi::c_void,
-						std::ptr::null_mut() as *const core::ffi::c_void,
+			call!(unsafe {
+				windows_sys::Win32::Storage::FileSystem::MoveFileExW(
+					path_to_windows_str(tmp_file_path).as_ptr(),
+					path_to_windows_str(dest_file_path).as_ptr(),
+					windows_sys::Win32::Storage::FileSystem::MOVEFILE_WRITE_THROUGH
+					| windows_sys::Win32::Storage::FileSystem::MOVEFILE_REPLACE_EXISTING,
 					)
-				});
-			} else {
-				call!(unsafe {
-					windows_sys::Win32::Storage::FileSystem::MoveFileExW(
-						path_to_windows_str(tmp_file_path).as_ptr(),
-						path_to_windows_str(dest_file_path).as_ptr(),
-						windows_sys::Win32::Storage::FileSystem::MOVEFILE_WRITE_THROUGH
-							| windows_sys::Win32::Storage::FileSystem::MOVEFILE_REPLACE_EXISTING,
-					)
-				});
-			}
+			});
 		}
 	}