One more attempt to fix the update function.

linux-game-manager.sh

@@ -51,15 +51,15 @@ check_update() {
     if [[ "$url" =~ ^ssh://|git@ ]] || [[ -z "$url" ]]; then
         return
     fi
-    git fetch
-    local branch="$(git rev-parse --abbrev-ref HEAD 2> /dev/null)"
-    local localSha="$(git rev-parse origin/${branch})"
-    local remoteSha="$(git rev-parse refs/remotes/origin/${branch})"
-    if [[ "${localSha}" == "${remoteSha}" ]]; then
-        return
-    fi
+    git remote update &> /dev/null
+    local upstream='@{u}'
+    local home="$(git rev-parse @)"
+    local remote="$(git rev-parse "$upstream")"
+if [[ "$home" == "$remote" ]]; then
+    return
+fi
     dialog --backtitle "Linux Game manager" \
-        --yesno "Updates are available. Would you like to update now?" -1 -1 || return
+        --yesno "Updates are available. Would you like to update now?" -1 -1 --stdout || return
     git pull
     exit $?
 }