narrow: move `only_show` handling sooner in `tracked`

This will help us to improve the locking scope in the `tracked` command.

hgext/narrow/narrowcommands.py

@@ -563,20 +563,9 b' def trackedcmd(ui, repo, remotepath=None'
         or update_working_copy
     )
 
-    oldincludes, oldexcludes = repo.narrowpats
-
-    # filter the user passed additions and deletions into actual additions and
-    # deletions of excludes and includes
-    addedincludes -= oldincludes
-    removedincludes &= oldincludes
-    addedexcludes -= oldexcludes
-    removedexcludes &= oldexcludes
-
-    widening = addedincludes or removedexcludes
-    narrowing = removedincludes or addedexcludes
-
     # Only print the current narrowspec.
     if only_show:
+        oldincludes, oldexcludes = repo.narrowpats
         ui.pager(b'tracked')
         fm = ui.formatter(b'narrow', opts)
         for i in sorted(oldincludes):
@@ -590,6 +579,18 b' def trackedcmd(ui, repo, remotepath=None'
         fm.end()
         return 0
 
+    oldincludes, oldexcludes = repo.narrowpats
+
+    # filter the user passed additions and deletions into actual additions and
+    # deletions of excludes and includes
+    addedincludes -= oldincludes
+    removedincludes &= oldincludes
+    addedexcludes -= oldexcludes
+    removedexcludes &= oldexcludes
+
+    widening = addedincludes or removedexcludes
+    narrowing = removedincludes or addedexcludes
+
     if update_working_copy:
         with repo.wlock(), repo.lock(), repo.transaction(
             b'narrow-wc'