tools: bpftool: fix bash completion for bpftool prog (attach|detach)

Fix bash completion for "bpftool prog (attach|detach) PROG TYPE MAP" so
that the list of indices proposed for MAP are map indices, and not PROG
indices. Also use variables for map and prog reference types ("id",
"pinned", and "tag" for programs).

Fixes: b7d3826c ("bpf: bpftool, add support for attaching programs to maps")
Signed-off-by: Quentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

tools/bpf/bpftool/bash-completion/bpftool

@@ -243,16 +243,20 @@ _bpftool()
     # Completion depends on object and command in use
     case $object in
         prog)
-            if [[ $command != "load" && $command != "loadall" ]]; then
+            # Complete id, only for subcommands that use prog (but no map) ids
+            case $command in
+                show|list|dump|pin)
                     case $prev in
                         id)
                             _bpftool_get_prog_ids
                             return 0
                             ;;
                     esac
-            fi
+                    ;;
+            esac
 
             local PROG_TYPE='id pinned tag'
+            local MAP_TYPE='id pinned'
             case $command in
                 show|list)
                     [[ $prev != "$command" ]] && return 0
@@ -293,23 +297,44 @@ _bpftool()
                     return 0
                     ;;
                 attach|detach)
-                    if [[ ${#words[@]} == 7 ]]; then
-                        COMPREPLY=( $( compgen -W "id pinned" -- "$cur" ) )
+                    case $cword in
+                        3)
+                            COMPREPLY=( $( compgen -W "$PROG_TYPE" -- "$cur" ) )
                             return 0
-                    fi
-
-                    if [[ ${#words[@]} == 6 ]]; then
-                        COMPREPLY=( $( compgen -W "msg_verdict skb_verdict \
-                            skb_parse flow_dissector" -- "$cur" ) )
+                            ;;
+                        4)
+                            case $prev in
+                                id)
+                                    _bpftool_get_prog_ids
+                                    ;;
+                                pinned)
+                                    _filedir
+                                    ;;
+                            esac
                             return 0
-                    fi
-
-                    if [[ $prev == "$command" ]]; then
-                        COMPREPLY=( $( compgen -W "id pinned" -- "$cur" ) )
+                            ;;
+                        5)
+                            COMPREPLY=( $( compgen -W 'msg_verdict skb_verdict \
+                                skb_parse flow_dissector' -- "$cur" ) )
                             return 0
-                    fi
+                            ;;
+                        6)
+                            COMPREPLY=( $( compgen -W "$MAP_TYPE" -- "$cur" ) )
+                            return 0
+                            ;;
+                        7)
+                            case $prev in
+                                id)
+                                    _bpftool_get_map_ids
+                                    ;;
+                                pinned)
+                                    _filedir
+                                    ;;
+                            esac
                             return 0
                             ;;
+                    esac
+                    ;;
                 load|loadall)
                     local obj