gitea-backup-pull: skip unmount (no error) if another process is busy on WSD2L840

rc.unassigned umount always does a lazy unmount and reports success
unconditionally, even with an open cwd on the mountpoint - it never
actually refuses on its own. Check with fuser -m first instead, and
just leave the disk mounted if anything is using it.

scripts/clients/vlda-01/user-scripts/gitea-backup-pull/script

@@ -56,11 +56,26 @@ DEL_BATCH=$(mktemp)
 cleanup() {
 	rm -f "$GET_BATCH" "$DEL_BATCH"
 	if [ "$UD_ALREADY_MOUNTED" = false ]; then
-		# cd out first - if the shell's own cwd is still on the device
-		# (it is, after the "cd $LOCAL_DIR" below), umount fails with
-		# "target is busy"
+		# cd out first - our own cwd on the device would otherwise
+		# make the fuser check below always find "something" using it
 		cd / || true
-		/usr/local/sbin/rc.unassigned umount "$UD_DEV" >/dev/null 2>&1
+
+		# rc.unassigned's umount always does a lazy (-l) unmount and
+		# reports "success" no matter what - it does NOT refuse or
+		# error out just because another process still has the
+		# mountpoint open (verified live: a process with its cwd on
+		# the device does not stop it, and does not get killed
+		# either, unless this were a forced "stop array"-style
+		# unmount, which a single-device call never is). So the only
+		# way to actually detect and respect another user of the
+		# disk is to check first, ourselves, and simply not attempt
+		# the unmount at all if anything is found - no ERROR, just
+		# leave it mounted for next time.
+		if fuser -m "$UD_MOUNTPOINT" >/dev/null 2>&1; then
+			echo "$(date -Is) $UD_MOUNTPOINT still in use by another process - leaving it mounted"
+		else
+			/usr/local/sbin/rc.unassigned umount "$UD_DEV" >/dev/null 2>&1
+		fi
 	fi
 }
 trap cleanup EXIT