Various maintainer notes:

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# Diagrams #
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the .dia files are source diagrams as generated by dia(1). It's a must
to store these files in the binary format when using svn, as they
contain xml and binary chunks . Automatically svn will store those as
text which will break binary strings making those files unusable.

So you either need to manually add the mime type property on each new
.dia file you add or adjust your ~/.subversion/config, to have:

[auto-props]
*.dia = svn:mime-type=application/octet-stream 

dia generates .png files via its export method. As older browsers
won't recognize .png or crash, we want to use gifs instead. Here is
how to convert png files to gif files:

  perl -le 'for (@ARGV) { print STDERR "converting $_\n"; \ s/\.\w+$//; \
     system "pngtopnm $_.png | pnmquant 256 | ppmtogif > $_.gif" } ' *.png