Improve mime-type detection

[giantclambake]

If XDG_DATA_HOME= "$username/.local/share", then it seems ~/.local/share/applications && ~/.local/share/mime/packages will likely exist. These locations represent 'User mode', and allow the user to customize various elements of the desktop environment ...ie; icons. In that case, the user can change/customize settings, as an extension of the System mode settings....ie; if the file ~/.local/share/mime/packages/amiberry.xml exists, and contains the snippet;

    <mime-type type="application/x-amiga--disk-image">
        <comment>Amiga disk image</comment>
        <generic-icon name="media-floppy"/>
        <glob pattern="*.adf"/>
    </mime-type>

Then the mime-type /usr/share/mime/packages/amiberry.xml is still used, but is overridden by ~/.local/share/mime/packages/amiberry.xml (User mode) to provide a different icon for the mime-type defined by System mode.

If XDG_DATA_HOME is unset/unused (Debian, Ubuntu)...then XDG_DATA_DIRS is used instead, and so everything has to be properly covered by /usr/share/mime/packages/amiberry.xml in this case...

....for /usr/share/mime/packages/amiberry.xml ;

<?xml version="1.0" encoding="UTF-8"?>
<mime-info xmlns="http://www.freedesktop.org/standards/shared-mime-info">
    <mime-type type="application/x-amiga-disk-image">
        <comment>Amiga disk image</comment>
        <generic-icon name="media-floppy"/>
        <magic priority="60">
        <match type="string" value="DOS\x0" offset="0"/>
        </magic>
        <glob pattern="*.adf"/>
    </mime-type>
    <mime-type type="application/x-SPS-virtual-media-image">
        <comment>Interchangeable Preservation Format</comment>
        <generic-icon name="media-floppy"/>
        <magic priority="50">
            <match type="string" value="CAPS" offset="0"/>
        </magic>
        <glob pattern="*.ipf"/>
    </mime-type>
    <mime-type type="application/x-DMS-compressed-disk-image">
        <comment>Disk Masher System</comment>
        <generic-icon name="media-floppy"/>
        <magic priority="50">
            <match type="string" value="DMS!" offset="0"/>
        </magic>
        <glob pattern="*.dms"/>
    </mime-type>
    <mime-type type="application/x-WHDLoad-game-archive">
        <comment>WHDLoad Amiga Package</comment>
        <generic-icon name="input-gaming"/>
        <magic-deleteall/>
        <magic priority="60">
            <match type="big32" value="0x001000084" offset="8:11"/>
        </magic>
        <glob-deleteall/>
        <glob pattern="*.lha"/>
    </mime-type>
</mime-info>

TIA

amiberry.xml.gz