[Bugs] #1551 UNSP: filestore.retrieve(): chmod() don't make sense

[Sugar Labs Bugs]

#1551: filestore.retrieve(): chmod() don't make sense
------------------------------------------+---------------------------------
    Reporter:  sascha_silbe               |          Owner:  tomeu                      
        Type:  defect                     |         Status:  new                        
    Priority:  Unspecified by Maintainer  |      Milestone:  Unspecified by Release Team
   Component:  sugar-datastore            |        Version:  Git as of bugdate          
    Severity:  Unspecified                |       Keywords:                             
Distribution:  Unspecified                |   Status_field:  Unconfirmed                
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 While fixing #1550, I stumbled over this code again:

 {{{
         # Try to hard link from the original file to the targetpath. This
 can
         # fail if the file is in a different filesystem. Do a symlink
 instead.
         try:
             os.link(file_path, destination_path)
         except OSError, e:
             if e.errno == errno.EXDEV:
                 os.symlink(file_path, destination_path)
             else:
                 raise

         # Try to make the original file readable. This can fail if the
 file is
         # in a FAT filesystem.
         try:
             os.chmod(file_path, 0604)
         except OSError, e:
             if e.errno != errno.EPERM:
                 raise
 }}}

 I guess the chmod() is supposed to make the file readable to the caller in
 case we use a symlink instead of a hardlink.
 The permissions don't make much sense:
 * allow read+write for the owner (data store user) - OK
 * no access to the group - ?
 * read access to world - overrides group settings

 Was it supposed to be 0640 (rw- r-- ---) instead?

 Why do we always do the chmod() instead of only when we actually symlink,
 BTW? A hardlink doesn't share permissions, only data.

 Do we support data stores on FAT filesystems at all? AFAICT our optimizer
 will fail hard (at least in filestore.hard_link_entry()) on those.

-- 
Ticket URL: <http://bugs.sugarlabs.org/ticket/1551>
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