fish_update_completions: pass explicit directory argument

Gets rid of another use of XDG_CACHE_HOME; this gets us closer to
a single source of truth. Not super important right now, but will
be helpful if we allow users to override XDG_CACHE_HOME in future.
I guess we could also remove it from create_manpage_completions.py,
that's unnecessary breakage but probably fine since this is not
public-facing.

share/functions/fish_update_completions.fish

@@ -16,9 +16,9 @@ function fish_update_completions --description "Update man-page based completion
         - \
         # Use the manpath
         --manpath \
+        --directory=$__fish_cache_dir/generated_completions \
         # Clean up old completions
-        --cleanup-in $__fish_user_data_dir/generated_completions \
-        --cleanup-in $__fish_cache_dir/generated_completions
+        --cleanup-in $__fish_user_data_dir/generated_completions
 
     status get-file tools/create_manpage_completions.py |
         if $detach

share/tools/create_manpage_completions.py

@@ -2231,6 +2231,7 @@ if __name__ == "__main__":
         args.directory = os.path.expanduser(
             xdg_cache_home + "/fish/generated_completions/"
         )
+    if not args.stdout:
         try:
             os.makedirs(args.directory)
         except OSError as e:

tests/checks/fish_update_completions.fish

@@ -24,7 +24,7 @@ end each output line with NUL, not newline
 '
 
 MANPATH=$PWD/man fish_update_completions
-# CHECK: Parsing man pages and writing completions to {{.*}}/generated_completions/
+# CHECK: Parsing man pages and writing completions to {{.*}}/generated_completions
 # CHECK: {{.*}}  1 / 1 : dirname.1{{.*}}
 
 cd $__fish_cache_dir