Wrong notification when a placeholder is renamed

[HanaGemela]

Client: 2.6.0alpha2 (build 12128)
macOS: 10.14.5
Server:10.2.1. (stable)

Steps to recreate:

1. Rename a file
2. Sync the file e.g. in different Account tab or on another machine that has VFS on so that the placeholder will be renamed

Actual result: User receives a notification that the old file has been removed and a new file has been added
Expected result: User receives a notification that the file has been renamed

[ogoffart]

It worked for me: the notification states that the file was moved.

[HanaGemela]

Still broken on 2.6.1-daily20191127 (build 12791), macOS 10.15.1 when syncing rename from Windows to Mac.
If the rename is synced from Mac to Windows, there is no notification at all on Windows.

[TheOneRing]

I think that issue sums up the current issue with the placeholder files.
We can't detect a move with placeholder files.

This lies in the nature of the current implementation.
Placeholder files hold no data, only the file name provides data.
If we would write the original file path and hash to the file, we could detect a move when encountering placeholder in a new location....

@ogoffart what do you think?