[Unison-hackers] Upgrade the unison stable version

[Sylvain Le Gall]

Hello,

On 06-10-2006, Benjamin Pierce <bcpierce at cis.upenn.edu> wrote:
>>>> Do you have an idea for a quick fix, for the 2.13.16 version ?
>>>
>>> Yes: Document the fact that Unison is not safe to use with removable
>>> media.
>>>
>>
>> Well, i could do that, but it is not really fair regarding the bug...
>
> I don't understand why you say that.  Unison is behaving exactly as  
> it is designed to behave and exactly as its documentation specifies.   
> The issue here is that, when a piece of removable storage goes  
> offline, the filesystem will tell Unison that all the files on it are  
> gone, and Unison will *correctly* (though, I agree, surprisingly)  
> delete all of them from the other replica.
>

Indeed, you are right, i am not saying that anything is wrong regarding
unison, i just try to say that it won't really solve the problem (even
if the problem is a correct behavior). 

>> If it is a question of time for working on the issue, i think i don't
>> made myself clear enough: i am not asking for a new version  
>> (because you
>> told me that it was not possible). I just need some information/ 
>> idea in
>> order for me to fix this. If unison just crash when encounting the
>> error on Unix/Linux, it will be enough for me...
>
> There was extensive discussion of possible solutions on this list a  
> few weeks ago.  The final proposed design was to add a preference for  
> specifying a "mount point" within the replicas (the default would be  
> just the empty path) that is expected always to exist on both hosts;  
> before any changes are transferred, this will be checked, and the run  
> will be aborted if it is missing.  Implementation of this idea should  
> be pretty easy.
>


OK, i go through the archive and try to make a plan to solve this bug.
Here it is :
- add an option to check presence of files/directories in the two root in
  the configuration file + command line,
- if a file is detected as deleted, check the presence of
  files/directories, to be sure the deletion doesn't come from a media
  disappearance,
- if one of the files/directories is not here -> abort,
- otherwise, continue,

There was also another approach where while scanning, you try to detect
the device number and remember it... Maybe it could also be used, as a
way to generate the files/directories option automatically ? I think
that unison open a dir before scanning the file, which could be used to
check the device number. So if a file under a particular mount point
need to be deleted, unison can check that the media is not gone. If all
the file are on the same mount point, it will default to the root dir.

So, i need to know what option name you want ?

If i produce a patch, do you think you should integrate it in unison ?

Any comments, suggestions ?

Regard
Sylvain Le Gall

ps: i hope you don't get upset about this, i really appreciate your work
on unison, which is a great software -- hope the content of my mail
doesn't suggest anything else.