[Unison-hackers] File copying/moving optimizations

[Derek Rayside]

On Wed, 2 Nov 2005, Jerry Haltom wrote:

> So I notice that Unison completely re-downloads a file when it is the
> result of a copy or a move. Makes sense from a simple implementation
> point of view, but I was wondering about an alternative.
>
> When a file is seen as not existing in the replica, it makes sense to me
> for the data of the file to be searched for in the replica, and copied
> to the new name if found. The original says a file with a certain MD5
> sum exists at a new location, the replicate searches for an existing
> file with that MD5 sum and copies it.
>
> Seems like this could speed up synchronization in some specific cases by
> a good deal. Simply renaming a large top level directory would result in
> a new directory being created in the replica and populated from the
> previous data. Much faster!
>
> Thoughts?


That would be a nice feature.  I wonder if it could be implemented without
threatening correctness.

My current work-around is to rename the top level directory on both
replicas:  it takes unison less time to figure out that the changes are
identical than it does to transfer the data.