As a response to: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=21008
 
It should be noted that if CSS3 isn't already touring complete, there are lots of CSS superset languages (LESS [1], SASS [2], etc) which definitely are touring-complete and whose Emacs-modes do derive from css-mode. As an emacs-user I would expect those modes to invoke my prog-mode hooks without me manually having to wire them up.
 
So I don't think there is any doubt that erring on the side of prog-mode is the right thing to do (tm).
 
While this isn't really a big deal to me, I agree with Vasilij that consistency would be nice.
 
As for file revision history, last time I checked git manages to track moved files just fine without messing up the history, so I don't see a technical reason to avoid fixing this up.
 
[1] https://github.com/myfreeweb/less-mode/blob/master/less-mode.el#L75
[2] https://github.com/antonj/scss-mode/blob/master/scss-mode.el#L87
 
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Jostein Kjønigsen
jostein@kjonigsen.net / jostein@secure.kjonigsen.net