Various maintainer notes:

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# Diagrams #
############

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. Really old browsers
don't recognize .png so it was previously recommended to convert the 
.png files to gifs.  However, all current browsers have acceptable png 
support, so you can leave them in that format.  If for some reason you
want to convert the files to gif, you can do it like this: 

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

pngtopnm, pnmquant, and ppmtogif are all part of netpbm, which is 
available at: 

http://netpbm.sourceforge.net/