[Unison-hackers] Extending the "rename" detection

[Isaac Witmer]

I know little about the unison code, but from my use, I've noticed
that it does seem to keep track of the files. On a few occasions,
unison has decided to recreate a file from another file that looked
similar that was already local. (my version of unison--2.32.52--has
the switch xferbycopying).

I wonder if in your case unison is attempting to delete files first,
and then when it gets around to xferbycopying, it doesn't have any
local copy to transfer from.

That pondering may be entirely useless to you. Hopefully someone else
knows what they're talking about more than me.

On Wed, Dec 5, 2012 at 3:44 PM, Nathan Thern <nthern at gmail.com> wrote:
> Hello -
> Longtime unison user. I have known for some time that renaming a file on one
> replica will result in a simple "copy-and-delete" operation at the target
> mirror replica when the two replicas are sync'd.
>
> Recently, I encountered a situation where several directories which
> contained large files were renamed on a replica. It happens to be a kind of
> "dropbox" folder for my family to put media content for me to download while
> I am traveling. I unison sync the folder rather than rsync it because I
> delete the content on my end as I consume it. My wife recently "helpfully"
> re-organized some of the directories in that folder and I found my unison
> process re-downloading big content that I actually already had because the
> directories had been "renamed". As unison saw it, some directories had been
> deleted and others added.
>
> So, I thought, "This could be a good addition to unison. Add a capability to
> compare newly deleted files to newly added files and detect that they are
> actually renames or moves across directories." I figured it would probably
> best be added as a new command-line option.
>
> I downloaded the source and started looking at it. I do not know ocaml, but
> was immediately impressed with the expressive power I could see.
> Unfortunately, I soon got lost in the code.
>
> Any hints on where to get started in the source to implement this? I'm
> currently working on learning ocaml, but I also want to get rolling on this
> project as soon as I can.
>
> regards,
> NT
>
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