Provide way to rename mime .xml files

[alexlarsson]

From @jurf on August 13, 2017 14:17

So we can stop doing things like:

"post-install": [
    "mv /app/share/mime/packages/scribus.xml /app/share/mime/packages/net.scribus.Scribus.xml"
]

Copied from original issue: flatpak/flatpak#958

[jurf]

This would also be great for mimetype icons, which currently have to be renamed manually and the new names have to be added to the xml file.

[hfiguiere]

This is much more complex. Renaming the mime .xml files. There is also renaming the icons for these mime type that otherwise don't get exported, but then the icon name should be set in the .xml file to match as this breaks the standard name of mime icons.

[hfiguiere]

We could have:

rename-mime: file.xml

This would rename the MIME .xml file

and also

rename-mime-icons: [ icon-name ]

This would act like rename icon, except it would rename to $FLATPAK_ID.icon-name and then modify the MIME .xml file to set the icon name.

[hfiguiere]

My proposed implementation in #567