bpftool: Add bash completion for program signing options

Commit 40863f4d6ef2 ("bpftool: Add support for signing BPF programs")
added new options for "bpftool prog load" and "bpftool gen skeleton".
This commit brings the relevant update to the bash completion file.

We rework slightly the processing of options to make completion more
resilient for options that take an argument.

Signed-off-by: Quentin Monnet <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

tools/bpf/bpftool/bash-completion/bpftool

···
     # Deal with options
     if [[ ${words[cword]} == -* ]]; then
         local c='--version --json --pretty --bpffs --mapcompat --debug \
-            --use-loader --base-btf'
+            --use-loader --base-btf --sign -i -k'
         COMPREPLY=( $( compgen -W "$c" -- "$cur" ) )
         return 0
     fi
···
             _sysfs_get_netdevs
             return 0
             ;;
-        file|pinned|-B|--base-btf)
+        file|pinned|-B|--base-btf|-i|-k)
             _filedir
             return 0
             ;;
···
     # Remove all options so completions don't have to deal with them.
     local i pprev
     for (( i=1; i < ${#words[@]}; )); do
-        if [[ ${words[i]::1} == - ]] &&
-            [[ ${words[i]} != "-B" ]] && [[ ${words[i]} != "--base-btf" ]]; then
-            words=( "${words[@]:0:i}" "${words[@]:i+1}" )
-            [[ $i -le $cword ]] && cword=$(( cword - 1 ))
-        else
-            i=$(( ++i ))
-        fi
+        case ${words[i]} in
+            # Remove option and its argument
+            -B|--base-btf|-i|-k)
+                words=( "${words[@]:0:i}" "${words[@]:i+2}" )
+                [[ $i -le $(($cword + 1)) ]] && cword=$(( cword - 2 ))
+                ;;
+            # No argument, remove option only
+            -*)
+                words=( "${words[@]:0:i}" "${words[@]:i+1}" )
+                [[ $i -le $cword ]] && cword=$(( cword - 1 ))
+                ;;
+            *)
+                i=$(( ++i ))
+                ;;
+        esac
     done
     cur=${words[cword]}
     prev=${words[cword - 1]}