[pacman-dev] difficult symlink puzzle, part 2.

[Andrew Fyfe]

Xavier wrote:
> On Fri, Aug 03, 2007 at 12:15:56AM +0200, Nagy Gabor wrote:
>> Hi!
>>
>> If I didn't misunderstood conflict.c then fileconflict check fails in the 
>> following case (pacman -A pkg1 pkg2):
>> pkg1 contains: /dir1/file
>> pkg2 contains: /dir2/file,
>> if /dir1 and /dir2 exists on filesystem, and /dir2 is a symlink pointing 
>> to /dir1.
>> Much more difficult problem (and fortunately much rarer), if pkg2 creates 
>> the /dir2 symlink, so it didn't exist before the transaction.
>> Any tests/feedbacks appreciated...
> 
> If it's possible to extend pactest for this stuff, it could probably help.
> 
>> How is this handled in other package managers?
>>
> 
> I tried to look at dpkg code, I didn't understand anything :p
> 
>> PS: a possible semi-solution: pacman shouldn't stop/overwrite in case of 
>> these "hidden" fileconflict errors, it extract /dir2/file as 
>> /dir2/file.pkg2.pacnew and do something at the end of the transaction. 
>> (Speed is a big limiting factor here.)
>>
>>
> 
> dpkg seems to use suffix as well, .dpkg-new and .dpkg-tmp. dpkg-new is
> apparently used for config files, and dpkg-tmp, I'm not sure.
> You can grep for these strings in dpkg source:
> http://ftp.debian.org/debian/pool/main/d/dpkg/dpkg_1.14.5.tar.gz
> 
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When installing a package dpkg moves the old file to *.dpkg-tmp, then 
extracts the new file (I think config files are extracted as .dpkg-new, 
can't remember off hand). Then the old file is removed later. This is a 
far better method than pacmans it allows dpkg to rollback a package 
install if there is an error.

Andrew