[pacman-dev] Remove directory symlink support in pacman-4.2 - Was: Use resolved paths for filelist operations

[Andrew Gregory]

On Mon, 18 Feb 2013 13:47:54 +1000
Allan McRae <allan at archlinux.org> wrote:

> On 18/02/13 12:52, Andrew Gregory wrote:
> > Having reviewed the related code far more than I never wanted to, I
> > believe I can get the number of resolved paths down to a manageable
> > level while keeping full symlink support.  We should be able to take
> > advantage of the fact that symlinks in paths are not the norm and file
> > basename collisions are actually quite rare to selectively resolve
> > individual paths as necessary instead of resolving whole filelists.  I
> > haven't worked out all of the specifics for doing this efficiently,
> > though, so it may not be worth it in the end.
> 
> It would be great if the amount of resolving could be reduced greatly.
> But what is a real use case for this feature?
> 

I was mostly just concerned about not removing functionality if we
don't really need to.  If there's really no need for it, I'm fine with
dropping it.

> > If we do remove support, we should probably at least still use resolved
> > paths to check for inter-target conflicts.  If one target has a symlink
> > in its paths I don't see any other way to catch a conflict prior to
> > actually extracting the files.  As long as we only resolve files that
> > are new in the package and packages don't constantly move files around,
> > this should have only a small performance hit most of the time.
> 
> I don't understand this.
> 
> A package can not have a symlink to a directory and files in the
> directory too. E.g. a package can not have /lib -> usr/lib and /lib/foo.
>  So there is no need to resolve there.
> 
> Or, a symlink one package and a directory is in the other would generate
> a conflict (as happens currently).  What would change is that we
> currently allow these to be installed in separate transactions (symlink
> containing package first).

Sorry, I meant that one of the packages has a directory that exists on
the filesystem as a symlink, for example:

filesystem:
/lib -> /usr/lib

pkg1:
/lib/foo

pkg2:
/usr/lib/foo

Without resolving /lib/foo we wouldn't be able to detect the conflict
until we started committing the transaction and actually tried to
extract the files.