It's named "image/x-panasonic-raw2" only in shared-mime-info while programs that can handle the files specify "image/x-panasonic-rw2". This will prevent applications from showing up in the "open with" dialog in every file browser. I tried to open a .rw2 file in dolphin with rawtherapee. I found out that also exiv2, ufraw, libopenraw (and others. Google will find them all) use x-panasonic-rw2.
It's been named that way since 51cbde9068b6528af8b01207c11172b72d78cc35, in November 2010, so I really don't see the point in changing it. Why do those programs make up their own mime-types? Do they ship mime-type definitions instead of using shared-mime-info's? Show me image/x-panasonic-rw2 being used before November 2010, and I'll make image/x-panasonic-rw2 the main mime-type. Otherwise, I'll just add image/x-panasonic-raw2 as an alias for the "correct" (read, oldest), mime-type.
exiv2 uses x-panasonic-rw2 in their wiki since Okt.1 2010: http://dev.exiv2.org/projects/exiv2/wiki/Supported_image_formats/13
commit 8cbd1a38b0bb0a62020984572fd5a33233245239 Author: Bastien Nocera <hadess@hadess.net> Date: Tue Mar 7 11:03:57 2017 +0100 Rename Panasonic RAW image mime-types to image/x-panasonic-rw* As used in exiv2 since October 2010, a couple of weeks before the mime-type was added to shared-mime-info: http://dev.exiv2.org/projects/exiv2/wiki/Supported_image_formats/13 This was likely a typo in the original definition. https://bugs.freedesktop.org/show_bug.cgi?id=100078
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