Update nanoc completion version 4.13.5

src/_nanoc

@@ -23,7 +23,7 @@
 # Description
 # -----------
 #
-#  Completion script for nanoc 4.12.16 (https://nanoc.app/)
+#  Completion script for nanoc 4.13.5 (https://nanoc.app/)
 #
 # ------------------------------------------------------------------------------
 # Authors
@@ -94,6 +94,7 @@ case $state in
         args=(
           {-W,--watch}'[watch for changes and recompile when needed]'
           "--diff[generate diff]"
+          "--focus=[compile only items matching the given pattern]:pattern"
         )
         ;;
       create-site)
@@ -111,7 +112,7 @@ case $state in
         )
         ;;
       prune)
-        args=(
+        args+=(
           {-n,--dry-run}"[print files to be deleted instead of actually deleting them]"
           {-y,--yes}"[confirm deletion]"
         )
@@ -122,8 +123,7 @@ case $state in
         )
         ;;
       show-data|show-plugins|show-rules)
-        args=(
-          )
+        args=()
         ;;
       view)
         args=(