bpftool: Add link bash completions

Extend bpftool's bash-completion script to handle new link command and its
sub-commands.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Reviewed-by: Quentin Monnet <quentin@isovalent.com>
Link: https://lore.kernel.org/bpf/20200429001614.1544-11-andriin@fb.com

tools/bpf/bpftool/bash-completion/bpftool

@@ -98,6 +98,12 @@ _bpftool_get_btf_ids()
         command sed -n 's/.*"id": \(.*\),$/\1/p' )" -- "$cur" ) )
 }
 
+_bpftool_get_link_ids()
+{
+    COMPREPLY+=( $( compgen -W "$( bpftool -jp link 2>&1 | \
+        command sed -n 's/.*"id": \(.*\),$/\1/p' )" -- "$cur" ) )
+}
+
 _bpftool_get_obj_map_names()
 {
     local obj
@@ -1082,6 +1088,39 @@ _bpftool()
                     ;;
             esac
             ;;
+        link)
+            case $command in
+                show|list|pin)
+                    case $prev in
+                        id)
+                            _bpftool_get_link_ids
+                            return 0
+                            ;;
+                    esac
+                    ;;
+            esac
+
+            local LINK_TYPE='id pinned'
+            case $command in
+                show|list)
+                    [[ $prev != "$command" ]] && return 0
+                    COMPREPLY=( $( compgen -W "$LINK_TYPE" -- "$cur" ) )
+                    return 0
+                    ;;
+                pin)
+                    if [[ $prev == "$command" ]]; then
+                        COMPREPLY=( $( compgen -W "$LINK_TYPE" -- "$cur" ) )
+                    else
+                        _filedir
+                    fi
+                    return 0
+                    ;;
+                *)
+                    [[ $prev == $object ]] && \
+                        COMPREPLY=( $( compgen -W 'help pin show list' -- "$cur" ) )
+                    ;;
+            esac
+            ;;
     esac
 } &&
 complete -F _bpftool bpftool