feat(auto-complete): :FzfLua completes options

It is possible to run nested options like so:
```
:FzfLua files winopts.fullscreen=true
```

- Requires nvim >= 0.7, below uses the old code
- Renamed `help_tags|man_pages` to `helptags|manpages`
  (backward compat, can still call `:FzfLua help_tags`
   but it will not show in auto-complete)

README.md

@@ -319,8 +319,8 @@ Alternatively, resuming work on a specific provider:
 | `resume`               | resume last command/query              |
 | `builtin`              | fzf-lua builtin commands               |
 | `profiles`             | fzf-lua configuration profiles         |
-| `help_tags`            | help tags                              |
-| `man_pages`            | man pages                              |
+| `helptags`             | help tags                              |
+| `manpages`             | man pages                              |
 | `colorschemes`         | color schemes                          |
 | `awesome_colorschemes` | Awesome Neovim color schemes           | 
 | `highlights`           | highlight groups                       |

lua/fzf-lua/core.lua

@@ -340,9 +340,7 @@ M.fzf = function(contents, opts)
     -- fzf 0.40 added 'zero' event for when there's no match
     -- clears the preview when there are no matching entries
     if opts.__FZF_VERSION and opts.__FZF_VERSION >= 0.40 and previewer.zero then
-      opts.keymap = opts.keymap or {}
-      opts.keymap.fzf = opts.keymap.fzf or {}
-      opts.keymap.fzf["zero"] = previewer:zero()
+      utils.map_set(opts, "keymap.fzf.zero", previewer:zero())
     end
     if opts.__FZF_VERSION
         and opts.__FZF_VERSION >= 0.46
@@ -361,9 +359,7 @@ M.fzf = function(contents, opts)
         tonumber(opts.winopts.preview.flip_columns),
         opts.winopts.preview.vertical,
         opts.winopts.preview.horizontal)
-      opts.keymap = opts.keymap or {}
-      opts.keymap.fzf = opts.keymap.fzf or {}
-      opts.keymap.fzf["resize"] = string.format("transform(%s)", transformer)
+      utils.map_set(opts, "keymap.fzf.resize", string.format("transform(%s)", transformer))
     end
     if type(previewer.preview_window) == "function" then
       -- do we need to override the preview_window args?

lua/fzf-lua/init.lua

@@ -222,6 +222,9 @@ do
     tabs = { "fzf-lua.providers.buffers", "tabs" },
     lines = { "fzf-lua.providers.buffers", "lines" },
     blines = { "fzf-lua.providers.buffers", "blines" },
+    helptags = { "fzf-lua.providers.helptags", "helptags" },
+    manpages = { "fzf-lua.providers.manpages", "manpages" },
+    -- backward compat
     help_tags = { "fzf-lua.providers.helptags", "helptags" },
     man_pages = { "fzf-lua.providers.manpages", "manpages" },
     colorschemes = { "fzf-lua.providers.colorschemes", "colorschemes" },
@@ -349,6 +352,11 @@ M._excluded_meta = {
   "get_info",
   "set_info",
   "get_last_query",
+  -- Exclude due to rename:
+  --   help_tags -> helptags
+  --   man_pages -> manpages
+  "help_tags",
+  "man_pages",
 }
 
 for _, m in ipairs(M._exported_modules) do

plugin/fzf-lua.lua

@@ -0,0 +1,82 @@
+if vim.g.loaded_fzf_lua == 1 then
+  return
+end
+vim.g.loaded_fzf_lua = 1
+
+-- Should never be called, below nvim 0.7 "plugin/fzf-lua.vim"
+-- sets `vim.g.loaded_fzf_lua=1`
+if vim.fn.has("nvim-0.7") ~= 1 then
+  vim.api.nvim_err_writeln("Fzf-lua minimum requirement is Neovim versions 0.5")
+  return
+end
+
+vim.api.nvim_create_user_command("FzfLua", function(opts)
+  require("fzf-lua.cmd").load_command(unpack(opts.fargs))
+end, {
+  nargs = "*",
+  complete = function(_, line)
+    local metatable = require("fzf-lua")
+    local builtin_list = vim.tbl_filter(function(k)
+      return metatable._excluded_metamap[k] == nil
+    end, vim.tbl_keys(metatable))
+
+    local l = vim.split(line, "%s+")
+    local n = #l - 2
+
+    if n == 0 then
+      local commands = vim.tbl_flatten({ builtin_list })
+      table.sort(commands)
+
+      return vim.tbl_filter(function(val)
+        return vim.startswith(val, l[2])
+      end, commands)
+    end
+
+    local defaults = require("fzf-lua.defaults").defaults
+    local cmd_opts = defaults[l[2]] or {}
+    local opts = vim.tbl_filter(function(k)
+      return not k:match("^_")
+    end, vim.tbl_keys(cmd_opts))
+
+    -- Flatten map's keys recursively
+    --   { a = { a1 = ..., a2 = ... } }
+    -- will be transformed to:
+    --   {
+    --     ["a.a1"] = ...,
+    --     ["a.a2"] = ...,
+    --   }
+    local function map_flatten(t, prefix)
+      if vim.tbl_isempty(t) then return {} end
+      local ret = {}
+      prefix = prefix and string.format("%s.", prefix) or ""
+      for k, v in pairs(t) do
+        if type(v) == "table" then
+          local inner = map_flatten(v)
+          for ki, vi in pairs(inner) do
+            ret[prefix .. k .. "." .. ki] = vi
+          end
+        else
+          ret[prefix .. k] = v
+        end
+      end
+      return ret
+    end
+
+    -- Add globals recursively, e.g. `winopts.fullscreen`
+    -- will be later retrieved using `utils.map_get(...)`
+    for _, k in ipairs({ "winopts", "keymap", "fzf_opts", "fzf_tmux_opts", "hls" }) do
+      opts = vim.tbl_flatten({ opts, vim.tbl_keys(map_flatten(defaults[k] or {}, k)) })
+    end
+
+    -- Add generic options that apply to all pickers
+    for _, o in ipairs({ "query" }) do
+      table.insert(opts, o)
+    end
+
+    table.sort(opts)
+
+    return vim.tbl_filter(function(val)
+      return vim.startswith(val, l[#l])
+    end, opts)
+  end,
+})

plugin/fzf-lua.vim

@@ -1,3 +1,8 @@
+" Neovim >= v0.7 uses 'plugin/fzf-lua.lua'
+if has('nvim-0.7')
+  finish
+end
+
 if !has('nvim-0.5')
     echohl Error
     echomsg "Fzf-lua is only available for Neovim versions 0.5 and above"