duplicate glob patterns in shared-mime-info

[Matthias Clasen]

Hey,

I tried to understand what goes wrong with the mime system to make
all .pcf fonts appear as Cisco VPN files in rawhide recently. I found
that somebody added a glob pattern

application/x-cisco-vpn-settings:*.pcf

but freedesktop.org.xml already contained a glob pattern for pcf fonts:

application/x-font-pcf:*.pcf

The way the current implementation (shared-mime-info and xdgmime) handle
duplicate globs is that update-mime-database warns about them and throws
all but the first one away, and xdgmime tries globs first before any
magic, and is satisfied when it finds a match. So for the .pcf pattern
update-mime-database only keeps the cisco-vpn pattern, and xdgmime
happily classifies every .pdf file as cisco-vpn. To fix this (and the
handling of duplicate globs in general), I propose to change the
implementations in the following way:

- update-mime-database should not throw away any glob patterns and
  just emit duplicates in the globs files. To handle duplicate glob
  patterns in the suffix tree inside the binary cache, we can just store
  them as children with a \0 character as follows:

   [p]
     [c]
        [f] - application/x-cisco-vpn-settings
           [\0] - application-x-font-pcf
           [\0] - some other mime type with glob *.pcf

- xdgmime should recognize if there are multiple mimetypes with the same
  glob, and use magic to disambiguate between them.

I'll attach patches for this. While I think they are correct, I would be
much more confident in them if we had a testsuite for the mime system...

Matthias


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