add completion for ar (#9720)

* add completion for ar

* clean the function

* update CHANGELOG

CHANGELOG.rst

@@ -31,6 +31,8 @@ Improved prompts
 
 Completions
 ^^^^^^^^^^^
+- Added completions for:
+  - ``ar`` (:issue:`9719`)
 - ``gcc`` completion descriptions have been clarified and shortened (:issue:`9722`).
 
 Improved terminal support

share/completions/ar.fish

@@ -0,0 +1,20 @@
+function __single
+    complete -f -c ar -n __fish_use_subcommand -a $argv[1] -d $argv[2] # no dash
+end
+
+__single d "Delete modules from the archive."
+__single m "move members in an archive."
+__single p "Print the specified members of the archive, to the standard output file."
+__single q "Quick append; Historically, add the files member... to the end of archive, without checking for replacement."
+__single r "Insert the files member... into archive (with replacement)."
+__single s "Add an index to the archive, or update it if it already exists."
+__single t "Display a table listing the contents of archive, or those of the files listed in member."
+__single x "Extract members (named member) from the archive."
+
+functions -e __single
+
+# TODO add mod
+# A number of modifiers (mod) may immediately follow the p keyletter, to specify variations on an operation's behavior:
+# add dash
+# command format
+# ar [emulation options] [-]{dmpqrstx}[abcDfilMNoOPsSTuvV] [--plugin <name>] [member-name] [count] archive-file file