I was looking at the web interface to SVN @ sourceforge - looking at recent changes (diffs). I found out that .dat files are considered to be binary, and thus no diff is shown. On the other hand .tab and .conf files are shown. See e.g. https://sourceforge.net/p/simutrans/code/1926/
If I do "svn diff" at my computer I can see diffs for .dat files normally.
Is that something we could change? Or might it be just my user setting of the web interface?
When checking in a dat file set it to svn:eol-style native
svn add xyz.dat
svn ps svn:eol-style native xyz.dat
You can use wildcards with them too.