Add support for metainfo.xml

[Rosalie241]

This adds support for metainfo.xml, appdata.xml is still supported though.

see https://www.freedesktop.org/software/appstream/docs/chap-Metadata.html#spec-component-location

[probonopd]

Thanks @Rosalie241. Not sure we want this ambiguity in AppImages, though. After all, if we allow 2 different file paths in AppImages, then all tools that verify AppImages or integrate them into the system would have to check 2 different file paths as well.

[Rosalie241]

Thanks @Rosalie241. Not sure we want this ambiguity in AppImages, though. After all, if we allow 2 different file paths in AppImages, then all tools that verify AppImages or integrate them into the system would have to check 2 different file paths as well.

Tools which want to support normal desktop applications that provide a metainfo/appdata.xml file will also have to check 2 paths though, so I'm not sure if it's a big problem, but I've updated my application (RMG) to use the new metainfo.xml file according to the freedesktop appstream documentation, and now the appimagetool cannot find the appstream data, which isn't ideal either.

[probonopd]

Maybe we should just put in a symlink? That would be backwards compatible.

[Rosalie241]

That could be an option but I'm not sure how to do that with the APIs available.

[probonopd]

Something roughly along these lines?

package main

import (
	"fmt"
	"log"
	"os"
)

func main() {
	metainfoPath := "usr/share/metainfo/metainfo.xml"
	appdataPath := "usr/share/metainfo/appdata.xml"

	// Check if metainfo.xml exists
	if _, err := os.Stat(metainfoPath); os.IsNotExist(err) {
		fmt.Println(metainfoPath, "does not exist, creating symlink to", appdataPath)

		// Create symlink from appdata.xml to metainfo.xml
		if err := os.Symlink(appdataPath, metainfoPath); err != nil {
			log.Fatalf("Failed to create symlink from %s to %s: %v", appdataPath, metainfoPath, err)
		} else {
			fmt.Println("Symlink created from", appdataPath, "to", metainfoPath)
		}
	} else {
		fmt.Println(metainfoPath, "exists")
	}

	// Check if appdata.xml exists
	if _, err := os.Stat(appdataPath); os.IsNotExist(err) {
		fmt.Println(appdataPath, "does not exist, creating symlink to", metainfoPath)

		// Create symlink from metainfo.xml to appdata.xml
		if err := os.Symlink(metainfoPath, appdataPath); err != nil {
			log.Fatalf("Failed to create symlink from %s to %s: %v", metainfoPath, appdataPath, err)
		} else {
			fmt.Println("Symlink created from", metainfoPath, "to", appdataPath)
		}
	} else {
		fmt.Println(appdataPath, "exists")
	}
}

[AsciiWolf]

FWIW, the "appdata.xml" suffix is deprecated and not used anymore by upstream. It is still supported for backwards compatibility, but should not be used for newer projects/packages.