Show booted profile name in MOTD

Derive the active profile from the btrfs subvolume mounted as root
(@desktop, @router, @TV-Media-Box, @minimal) and show it in the MOTD,
so it is obvious which profile a session booted into.

Author: Yury-MonZon

overlays/configs/update-motd.d/00-flipperone

@@ -15,13 +15,20 @@ build_git=${BUILD_GIT:-unknown}
 
 total_mem=$(awk '/MemTotal/ {printf "%.1f GB", $2/1024/1024}' /proc/meminfo)
 
+# Currently booted profile = the btrfs subvolume mounted as root (@Desktop,
+# @Router, @TV-Media-Box, @Minimal). "/@Foo" -> "Foo"; non-subvolume -> unknown.
+profile=$(findmnt -nro FSROOT / 2>/dev/null)
+profile=${profile#/}
+[ -n "$profile" ] && [ "$profile" != "/" ] || profile=unknown
+
 # Generate MOTD
 cat <<EOF
 
                     Welcome to FlipperOne
 
    Git:          $build_git
    Board:        $board
+   Profile:      $profile
    CPU Serial:   $serial
    Memory:       $total_mem
    Build ID:     $build_id