VCS::FileInBranch#pull can encounter strange race conditions

[FinnWoelm]

On Google Drive, given a folder folder 1 with a file file A inside. Then file A is moved out of folder 1 into folder 2. And folder 1 is deleted.

Both folder 1 and file A are currently loaded into memory.

When folder 1 is pulled, it is marked as deleted and so are its current children, including file A. When file A is pulled afterwards, all its attributes remain unchanged except for its parent (now folder 2). So when we call #save, it updates only parent in the database — not the other attributes. So in the database file A remains incorrectly marked as deleted.

We can fix this by either marking all force-update fields as dirty: name_will_change! and parent_id_will_change! etc...

Or we can drop those fields completely and use just current_version_id for inheriting those fields (and forcing current_version_id to update by marking it as dirty!)