Strange LINGUAS in GIMP quick reference makefile

[Ask Hjorth Larsen <asklarsen gmail com>]

Hello

In the GIMP quick reference, the Makefile.am contains:

ALL_LINGUAS ?= de el en es fr it ja ko nl nn ru sl sv zh_CN
QUICKREFERENCE_ALL_LINGUAS ?= ca de el en fi fr it ja ko pl ru sv zh_CN
QUICKREFERENCE_LINGUAS = $(filter $(ALL_LINGUAS), $(QUICKREFERENCE_ALL_LINGUAS))

I am not really an expert in make, and I would like to add Danish,
'da'.  To which of the two lists should 'da' be added, or should it be
added to both?  And why?

I notice that most languages are listed in both, but ca is only in the
second, and es is only in the first.  Might this be an error?

Best regards
Ask