Comment 1 for bug 1579528

I would like to second this request by adding a bit more insight: without the copyright notice, `appstream-util validate-strict your.appdata.xml` fails with a warning. This is even one of the reasons why we cannot check our (GIMP's) appdata file with strict validation in our unit tests, and I am thinking maybe I should do some after-intltool-merge script which would add back the copyright comment (technically easy, but still ugly, hence annoying).

What would be very nice would be either a `--keep-comments` (or other naming, I don't care) option to not strip comments out, or a `--appdata-style` which would strip all comments except the copyright one (since this one is nearly part of the format).

Or ideally both (--appdata-style is nicer for our specific case, but I could imagine `--keep-comments` would be useful in future cases of other formats we don't think about).