Add AppStream support for Linux and BSD

.editorconfig

@@ -15,6 +15,11 @@ charset = utf-8
 indent_style = space
 indent_size = 3
 
+# 2 space indentation
+[*.{json,xml,yaml,yml}]
+indent_style = space
+indent_size = 2
+
 # Tab indentation
 [Makefile*]
 indent_style = tab

Makefile

@@ -235,6 +235,7 @@ install: $(TARGET)
 	cp $(TARGET) $(DESTDIR)$(BIN_DIR)
 	cp tools/cg2glsl.py $(DESTDIR)$(BIN_DIR)/retroarch-cg2glsl
 	cp retroarch.cfg $(DESTDIR)$(GLOBAL_CONFIG_DIR)
+	cp com.libretro.RetroArch.appdata.xml $(DESTDIR)$(DATA_DIR)/metainfo
 	cp retroarch.desktop $(DESTDIR)$(DATA_DIR)/applications
 	cp docs/retroarch.6 $(DESTDIR)$(MAN_DIR)/man6
 	cp docs/retroarch-cg2glsl.6 $(DESTDIR)$(MAN_DIR)/man6
@@ -245,6 +246,7 @@ install: $(TARGET)
 	chmod 755 $(DESTDIR)$(BIN_DIR)/retroarch-cg2glsl
 	chmod 644 $(DESTDIR)$(GLOBAL_CONFIG_DIR)/retroarch.cfg
 	chmod 644 $(DESTDIR)$(DATA_DIR)/applications/retroarch.desktop
+	chmod 644 $(DESTDIR)$(DATA_DIR)/metainfo/com.libretro.RetroArch.appdata.xml
 	chmod 644 $(DESTDIR)$(MAN_DIR)/man6/retroarch.6
 	chmod 644 $(DESTDIR)$(MAN_DIR)/man6/retroarch-cg2glsl.6
 	chmod 644 $(DESTDIR)$(DATA_DIR)/pixmaps/retroarch.svg
@@ -269,6 +271,7 @@ uninstall:
 	rm -f $(DESTDIR)$(BIN_DIR)/retroarch-cg2glsl
 	rm -f $(DESTDIR)$(GLOBAL_CONFIG_DIR)/retroarch.cfg
 	rm -f $(DESTDIR)$(DATA_DIR)/applications/retroarch.desktop
+	rm -f $(DESTDIR)$(DATA_DIR)/metainfo/com.libretro.RetroArch.appdata.xml
 	rm -f $(DESTDIR)$(DATA_DIR)/pixmaps/retroarch.svg
 	rm -f $(DESTDIR)$(DOC_DIR)/COPYING
 	rm -f $(DESTDIR)$(DOC_DIR)/COPYING.assets

com.libretro.RetroArch.appdata.xml

@@ -0,0 +1,48 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<component type="desktop">
+  <id>com.libretro.RetroArch</id>
+  <launchable type="desktop-id">retroarch.desktop</launchable>
+  <metadata_license>CC0-1.0</metadata_license>
+  <name>RetroArch</name>
+  <summary>Frontend for emulators, game engines and media players</summary>
+  <description>
+    <p>
+      RetroArch is an open source and cross platform frontend/framework for emulators, game engines, video games, media players and other applications.
+    </p>
+    <p>
+      While it can do many things besides this, it is most widely known for enabling you to run classic games on a wide range of computers and consoles through a slick graphical interface. Settings are also unified so configuration is done once and for all.
+    </p>
+    <p>
+      In addition to this, you will soon be able to run original game discs (CDs) from RetroArch. We take videogame preservation seriously and want to ensure you can run your originally bought content on modern day PCs.
+    </p>
+    <p>
+      RetroArch has advanced features like shaders, netplay, rewinding, next-frame response times, runahead, and more!
+    </p>
+  </description>
+  <url type="homepage">https://www.retroarch.com/</url>
+  <url type="bugtracker">https://github.com/libretro/RetroArch/issues</url>
+  <url type="donation">https://www.retroarch.com/index.php?page=donate</url>
+  <releases>
+    <release version="1.8.9"/>
+  </releases>
+  <project_group>Libretro</project_group>
+  <project_license>GPL-3.0</project_license>
+  <developer_name>Libretro</developer_name>
+  <screenshots>
+    <screenshot type="default">
+      <image>https://www.retroarch.com/images/xmb-tabs.png</image>
+    </screenshot>
+    <screenshot type="default">
+      <image>https://www.retroarch.com/images/xmb-updater.png</image>
+    </screenshot>
+    <screenshot type="default">
+      <image>https://www.retroarch.com/images/xmb-osk.png</image>
+    </screenshot>
+    <screenshot type="default">
+      <image>https://www.retroarch.com/images/xmb-playlists.png</image>
+    </screenshot>
+    <screenshot type="default">
+      <image>https://www.retroarch.com/images/xmb-metadata.png</image>
+    </screenshot>
+  </screenshots>
+</component>