Withhold the show key from a key the command binds

Setting show_key to a key a command binds for its own hint, ctrl-alt-x on
Buffers or alt-a on Rg, advertised both in the footer while the command's
binding won by coming later in the options. '_hint' entries now carry the
fzf key names behind the label, which is what the check compares, since a
label like 'A-a/d' cannot be.

autoload/fzf/vim.vim

@@ -371,8 +371,8 @@ function! s:build_hint(entries, defaults, ...)
       endif
     endfor
   endif
-  for [key, action] in entries
-    call add(keys, s:magenta(key, 'Special').' '.action)
+  for entry in entries
+    call add(keys, s:magenta(entry[0], 'Special').' '.entry[1])
   endfor
   return join(keys, '  ')
 endfunction
@@ -801,7 +801,7 @@ endfunction
 " Whether the show key can be offered for this run. Decided from the merged
 " spec, since the layout can arrive with the per-call spec, and a bang puts
 " fzf on its own tabpage where the window we would open in is not visible.
-function! s:can_show(spec, bang, key) abort
+function! s:can_show(spec, bang, key, claimed) abort
   " Older fzf blocks Vim in popup and fullscreen modes, so the callback would
   " only run after fzf exits, overriding whatever was selected. fzf#run is
   " only asynchronous when it has a terminal to put fzf in, and win32unix
@@ -816,12 +816,13 @@ function! s:can_show(spec, bang, key) abort
     return 0
   endif
   " fzf matches --expect before the key bindings, so an action or the paste
-  " key would win over ours. Any key of the list losing disables all of them,
-  " so that the footer cannot advertise a key that does nothing
+  " key would win over ours, and a key the command binds itself would win by
+  " coming later in the options. Any key of the list losing disables all of
+  " them, so that the footer cannot advertise a key that does nothing
   let actions = get(g:, 'fzf_action', s:default_action)
   let paste = s:split_keys(s:paste_key())
   for key in s:split_keys(a:key)
-    if has_key(actions, key) || index(paste, key) >= 0
+    if has_key(actions, key) || index(paste, key) >= 0 || index(a:claimed, key) >= 0
       return 0
     endif
   endfor
@@ -844,7 +845,9 @@ function! s:can_show(spec, bang, key) abort
 endfunction
 
 " Installs the show key binding and the key hint footer. '_show' names the entry
-" kind, '_hint' opts in to the footer and carries the command's own keys.
+" kind, '_hint' opts in to the footer and carries the command's own keys as
+" [label, description] or [label, description, keys]. The fzf key names in
+" 'keys' are what the show key is checked against, since the label cannot be.
 " Returns the fifo of the ipc channel it started, so the caller can stop it if
 " the run never reaches 'exit'
 function! s:add_hints(spec, bang) abort
@@ -852,8 +855,16 @@ function! s:add_hints(spec, bang) abort
   let taken = []
   let kind = s:pluck(a:spec, '_show', '')
   let entries = s:pluck(a:spec, '_hint', 0)
+  let claimed = []
+  if type(entries) == s:TYPE.list
+    for entry in entries
+      for name in get(entry, 2, [])
+        call extend(claimed, s:split_keys(name))
+      endfor
+    endfor
+  endif
   let key = s:show_key()
-  if !empty(kind) && !empty(key) && s:can_show(a:spec, a:bang, key)
+  if !empty(kind) && !empty(key) && s:can_show(a:spec, a:bang, key, claimed)
     let dir = get(a:spec, 'dir', '')
     let fifo = fzf#vim#ipc#start(function('s:show_entry',
           \ [win_getid(), empty(dir) ? getcwd() : dir, kind]))
@@ -1347,7 +1358,7 @@ function! fzf#vim#buffers(...)
   \ '_paste':  1
   \}
   let spec._show = 'buffer'
-  let spec._hint = [['C-A-X', 'Unload']]
+  let spec._hint = [['C-A-X', 'Unload', ['ctrl-alt-x']]]
   let options = ['+m', '-x', '--tiebreak=index', '--ansi', '-d', '\t', '--with-nth', '3..', '-n', '2,1..2', '--prompt', 'Buf> ', '--query', query, '--preview-window', '+{2}/2', '--tabstop', tabstop, '--bind', 'ctrl-alt-x:execute-silent(echo {} >> '.fzf#shellescape(delete_file).')+exclude']
   if bufnr('') == first
     call extend(options, ['--sync', '--bind', 'start:pos:2'])
@@ -1473,7 +1484,7 @@ function! fzf#vim#grep(grep_command, ...)
 
   let opts._paste = 1
   let opts._show = 'grep'
-  let opts._hint = [['A-a/d', 'Select/deselect all']]
+  let opts._hint = [['A-a/d', 'Select/deselect all', ['alt-a', 'alt-d']]]
   function! opts.sink(lines) closure
     return s:ag_handler(get(opts, 'name', name), a:lines)
   endfunction
@@ -1521,7 +1532,7 @@ function! fzf#vim#grep2(command_prefix, query, ...)
   endif
   let opts._paste = 1
   let opts._show = 'grep'
-  let opts._hint = [['A-a/d', 'Select/deselect all']]
+  let opts._hint = [['A-a/d', 'Select/deselect all', ['alt-a', 'alt-d']]]
   function! opts.sink(lines) closure
     return s:ag_handler(name, a:lines)
   endfunction