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Posted to dev@subversion.apache.org by Phillip Susi <ps...@cfl.rr.com> on 2005/04/25 21:55:18 UTC

Junction Point bug report and possible solution

I found a bug with subversion and NTFS Junction points, which are NT 
versions of symbolic links for directories.  The problem may also apply 
to symbolic links on unix.  I also think I have found the cause of the 
problem in the source, and a way to fix it, so I am posting my findings 
here in hopes that a developer can verify and apply them.

Background:

If you check out a working copy to c:\wc then create a junction called 
c:\junction that points to c:\wc, then you cd \junction and run svn 
status, it reports "." with a "~" status, indicating that it thinks the 
current directory is a file, not a directory.  TortoisSVN also will not 
treat c:\junction as a working copy.

Cause:

subversion/libsvn_subr/io.c line 137 reads:

   else if (finfo.filetype == APR_LNK)
     {
       is_special = TRUE;
       *kind = svn_node_file;
     }

I believe the bug is here.  The code calls apr_stat with the 
APR_FINFO_LINK flag, and apr_stat returns a file type of APR_LNK because 
the file in question is a symbolic link.  The above code assumes that a 
symbolic link points to a file, not a directory.  This assumption is 
incorrect, as symbolic links can also point to directories.

Solution:

When apr_stat indicates APR_LNK on the file, is_special should be set to 
true, and then apr_stat should be called again WITHOUT the 
APR_FINFO_LINK flag, which will cause it to indicate APR_REG or APR_DIR 
depending on weather the link points to a file or a directory.  That 
value should then be used to set *kind to svn_node_file or svn_node_dir.



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Re: Symlink handling in svn status broken

Posted by Aleksey Nogin <al...@nogin.org>.

On 22.09.2005 11:06, Philip Martin wrote:

> Phillip Susi <ps...@cfl.rr.com> writes:
> 
> 
>>Try this:
>>
>>svnadmin create repo
>>svn co file://`pwd`/repo wc
>>svn mkdir wc/trunk
>>svn ci -m "" wc
>>cd wc
>>mv trunk ..
>>ln -s ../trunk trunk
>>svn st
>>
>>The key thing is to be in the wc directory which has a .svn/entries
>>file that says it should have a child directory named trunk.  Trunk
>>gets moved elsewhere and replaced with a symlink, then when you do an
>>svn st, it thinks that trunk is a file but should be a directory, so
>>it reports it as a collision.
> 
> 
> I'm not sure that qualifies as a bug, you are disrupting the versined
> filesystem.  Subversion assumes that versioned files are files and
> that versioned directories are directories.  If you deliberately break
> those assumptions it's not surprising things don't work.
> 
Still, sometimes it's very useful to be able to relocate a part of a wc 
(say, to a different partition), replacing it with a symlink. IMHO it 
would be very nice if this would be supported.

-- 
Aleksey Nogin

Home Page: http://nogin.org/
E-Mail: nogin@cs.caltech.edu (office), aleksey@nogin.org (personal)
Office: Moore 04, tel: (626) 395-2200

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Re: Symlink handling in svn status broken

Posted by Greg Hudson <gh...@MIT.EDU>.

On Thu, 2005-09-22 at 14:29 -0400, Phillip Susi wrote:
> The versioned directory IS still a directory, it just has been moved and 
> replaced with a symbolic link to the new location.  Shouldn't subversion 
> follow the symbolic link transparently to the versioned directory?

We version symlinks these days.  To Subversion, this looks a lot like
the directory has been replaced with something else.  (Although without
a corresponding "svn rm" and "svn add" it looks to Subversion like it
has been replaced incorrectly.)

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