Generalize update command

fish/functions/macos_update.fish

@@ -1,5 +0,0 @@
-function macos_update
-    brew upgrade
-    gup update
-    cargo install-update --all
-end

fish/functions/update.fish

@@ -0,0 +1,25 @@
+function update
+    switch (uname)
+        case Linux
+            if type -q yay
+                yay
+            end
+
+            if type -q flatpak
+                flatpak update
+            end
+        case Darwin
+            brew upgrade
+        case '*'
+            echo "Unsupported OS"
+            exit 1
+    end
+
+    if type -q gup
+        gup update
+    end
+
+    if type -q cargo
+        cargo install-update --all
+    end
+end