feat(help): Help panel popup

README.md

@@ -318,6 +318,10 @@ require("diffview").setup({
       { "n", "<tab>", actions.select_entry,  { desc = "Change the current option" } },
       { "n", "q",     actions.close,         { desc = "Close the panel" } },
     },
+    help_panel = {
+      { "n", "q",     actions.close,  { desc = "Close help menu" } },
+      { "n", "<esc>", actions.close,  { desc = "Close help menu" } },
+    },
   },
 })
 ```

doc/diffview_defaults.txt

@@ -172,6 +172,10 @@ require("diffview").setup({
       { "n", "<tab>", actions.select_entry,  { desc = "Change the current option" } },
       { "n", "q",     actions.close,         { desc = "Close the panel" } },
     },
+    help_panel = {
+      { "n", "q",     actions.close,  { desc = "Close help menu" } },
+      { "n", "<esc>", actions.close,  { desc = "Close help menu" } },
+    },
   },
 })
 

lua/diffview/actions.lua

@@ -1,6 +1,7 @@
 local lazy = require("diffview.lazy")
 
 local DiffView = lazy.access("diffview.scene.views.diff.diff_view", "DiffView") ---@type DiffView|LazyModule
+local HelpPanel = lazy.access("diffview.ui.panels.help_panel", "HelpPanel") ---@type HelpPanel|LazyModule
 local FileHistoryView = lazy.access("diffview.scene.views.file_history.file_history_view", "FileHistoryView") ---@type FileHistoryView|LazyModule
 local StandardView = lazy.access("diffview.scene.views.standard.standard_view", "StandardView") ---@type StandardView|LazyModule
 local vcs = lazy.require("diffview.vcs.utils") ---@module "diffview.vcs.utils"
@@ -465,6 +466,17 @@ function M.cycle_layout()
   end
 end
 
+function M.help(conf_name)
+  return function()
+    local view = lib.get_current_view()
+
+    if view then
+      local help_panel = HelpPanel(view, conf_name) --[[@as HelpPanel ]]
+      help_panel:focus()
+    end
+  end
+end
+
 local action_names = {
   "close",
   "close_all_folds",

lua/diffview/config.lua

@@ -94,6 +94,11 @@ M.defaults = {
       win_opts = {}
     },
   },
+  help_panel = {
+    win_config = {
+      win_opts = {}
+    },
+  },
   default_args = {
     DiffviewOpen = {},
     DiffviewFileHistory = {},
@@ -120,6 +125,7 @@ M.defaults = {
       { "n", "<leader>cb", actions.conflict_choose("base"),    { desc = "Choose the BASE version of a conflict" } },
       { "n", "<leader>ca", actions.conflict_choose("all"),     { desc = "Choose all the versions of a conflict" } },
       { "n", "dx",         actions.conflict_choose("none"),    { desc = "Delete the conflict region" } },
+      { "n", "g?",         actions.help("view"),               { desc = "Open the help panel" } },
     },
     diff1 = { --[[ Mappings in single window diff layouts ]] },
     diff2 = { --[[ Mappings in 2-way diff layouts ]] },
@@ -162,35 +168,42 @@ M.defaults = {
       { "n", "g<C-x>",        actions.cycle_layout,         { desc = "Cycle available layouts" } },
       { "n", "[x",            actions.prev_conflict,        { desc = "Go to the previous conflict" } },
       { "n", "]x",            actions.next_conflict,        { desc = "Go to the next conflict" } },
+      { "n", "g?",            actions.help("file_panel"),   { desc = "Open the help panel" } },
     },
     file_history_panel = {
-      { "n", "g!",            actions.options,             { desc = "Open the option panel" } },
-      { "n", "<C-A-d>",       actions.open_in_diffview,    { desc = "Open the entry under the cursor in a diffview" } },
-      { "n", "y",             actions.copy_hash,           { desc = "Copy the commit hash of the entry under the cursor" } },
-      { "n", "L",             actions.open_commit_log,     { desc = "Show commit details" } },
-      { "n", "zR",            actions.open_all_folds,      { desc = "Expand all folds" } },
-      { "n", "zM",            actions.close_all_folds,     { desc = "Collapse all folds" } },
-      { "n", "j",             actions.next_entry,          { desc = "Bring the cursor to the next file entry" } },
-      { "n", "<down>",        actions.next_entry,          { desc = "Bring the cursor to the next file entry" } },
-      { "n", "k",             actions.prev_entry,          { desc = "Bring the cursor to the previous file entry." } },
-      { "n", "<up>",          actions.prev_entry,          { desc = "Bring the cursor to the previous file entry." } },
-      { "n", "<cr>",          actions.select_entry,        { desc = "Open the diff for the selected entry." } },
-      { "n", "o",             actions.select_entry,        { desc = "Open the diff for the selected entry." } },
-      { "n", "<2-LeftMouse>", actions.select_entry,        { desc = "Open the diff for the selected entry." } },
-      { "n", "<c-b>",         actions.scroll_view(-0.25),  { desc = "Scroll the view up" } },
-      { "n", "<c-f>",         actions.scroll_view(0.25),   { desc = "Scroll the view down" } },
-      { "n", "<tab>",         actions.select_next_entry,   { desc = "Open the diff for the next file" } },
-      { "n", "<s-tab>",       actions.select_prev_entry,   { desc = "Open the diff for the previous file" } },
-      { "n", "gf",            actions.goto_file,           { desc = "Open the file in a new split in the previous tabpage" } },
-      { "n", "<C-w><C-f>",    actions.goto_file_split,     { desc = "Open the file in a new split" } },
-      { "n", "<C-w>gf",       actions.goto_file_tab,       { desc = "Open the file in a new tabpage" } },
-      { "n", "<leader>e",     actions.focus_files,         { desc = "Bring focus to the file panel" } },
-      { "n", "<leader>b",     actions.toggle_files,        { desc = "Toggle the file panel" } },
-      { "n", "g<C-x>",        actions.cycle_layout,        { desc = "Cycle available layouts" } },
+      { "n", "g!",            actions.options,                     { desc = "Open the option panel" } },
+      { "n", "<C-A-d>",       actions.open_in_diffview,            { desc = "Open the entry under the cursor in a diffview" } },
+      { "n", "y",             actions.copy_hash,                   { desc = "Copy the commit hash of the entry under the cursor" } },
+      { "n", "L",             actions.open_commit_log,             { desc = "Show commit details" } },
+      { "n", "zR",            actions.open_all_folds,              { desc = "Expand all folds" } },
+      { "n", "zM",            actions.close_all_folds,             { desc = "Collapse all folds" } },
+      { "n", "j",             actions.next_entry,                  { desc = "Bring the cursor to the next file entry" } },
+      { "n", "<down>",        actions.next_entry,                  { desc = "Bring the cursor to the next file entry" } },
+      { "n", "k",             actions.prev_entry,                  { desc = "Bring the cursor to the previous file entry." } },
+      { "n", "<up>",          actions.prev_entry,                  { desc = "Bring the cursor to the previous file entry." } },
+      { "n", "<cr>",          actions.select_entry,                { desc = "Open the diff for the selected entry." } },
+      { "n", "o",             actions.select_entry,                { desc = "Open the diff for the selected entry." } },
+      { "n", "<2-LeftMouse>", actions.select_entry,                { desc = "Open the diff for the selected entry." } },
+      { "n", "<c-b>",         actions.scroll_view(-0.25),          { desc = "Scroll the view up" } },
+      { "n", "<c-f>",         actions.scroll_view(0.25),           { desc = "Scroll the view down" } },
+      { "n", "<tab>",         actions.select_next_entry,           { desc = "Open the diff for the next file" } },
+      { "n", "<s-tab>",       actions.select_prev_entry,           { desc = "Open the diff for the previous file" } },
+      { "n", "gf",            actions.goto_file,                   { desc = "Open the file in a new split in the previous tabpage" } },
+      { "n", "<C-w><C-f>",    actions.goto_file_split,             { desc = "Open the file in a new split" } },
+      { "n", "<C-w>gf",       actions.goto_file_tab,               { desc = "Open the file in a new tabpage" } },
+      { "n", "<leader>e",     actions.focus_files,                 { desc = "Bring focus to the file panel" } },
+      { "n", "<leader>b",     actions.toggle_files,                { desc = "Toggle the file panel" } },
+      { "n", "g<C-x>",        actions.cycle_layout,                { desc = "Cycle available layouts" } },
+      { "n", "g?",            actions.help("file_history_panel"),  { desc = "Open the help panel" } },
     },
     option_panel = {
-      { "n", "<tab>", actions.select_entry,  { desc = "Change the current option" } },
-      { "n", "q",     actions.close,         { desc = "Close the panel" } },
+      { "n", "<tab>", actions.select_entry,          { desc = "Change the current option" } },
+      { "n", "q",     actions.close,                 { desc = "Close the panel" } },
+      { "n", "g?",    actions.help("option_panel"),  { desc = "Open the help panel" } },
+    },
+    help_panel = {
+      { "n", "q",     actions.close,  { desc = "Close help menu" } },
+      { "n", "<esc>", actions.close,  { desc = "Close help menu" } },
     },
   },
 }

lua/diffview/ui/panels/help_panel.lua

@@ -0,0 +1,165 @@
+local Panel = require("diffview.ui.panel").Panel
+local get_user_config = require("diffview.config").get_config
+local oop = require("diffview.oop")
+local utils = require("diffview.utils")
+
+local api = vim.api
+
+local M = {}
+
+---@class HelpPanel : Panel
+---@field keymap_name string
+---@field lines string[]
+---@field maps table[]
+local HelpPanel = oop.create_class("HelpPanel", Panel)
+
+HelpPanel.winopts = vim.tbl_extend("force", Panel.winopts, {
+  wrap = false,
+  breakindent = true,
+  signcolumn = "no",
+})
+
+HelpPanel.bufopts = vim.tbl_extend("force", Panel.bufopts, {
+  buftype = "nofile",
+})
+
+HelpPanel.default_type = "float"
+
+---@class HelpPanelSpec
+---@field parent StandardView
+---@field config PanelConfig
+---@field name string
+
+---@param parent StandardView
+---@param keymap_name string
+---@param opt HelpPanelSpec
+function HelpPanel:init(parent, keymap_name, opt)
+  opt = opt or {}
+  HelpPanel:super().init(self, {
+    bufname = opt.name,
+    config = opt.config or get_user_config().help_panel.win_config,
+  })
+
+  self.parent = parent
+  self.keymap_name = keymap_name
+  self.lines = {}
+
+  self:on_autocmd("BufWinEnter", {
+    callback = function()
+      vim.bo[self.bufid].bufhidden = "wipe"
+    end,
+  })
+
+  self:on_autocmd("WinLeave", {
+    callback = function()
+      pcall(self.close, self)
+    end,
+  })
+
+  parent.emitter:on("close", function(e)
+    if self:is_focused() then
+      pcall(self.close, self)
+      e:stop_propagation()
+    end
+  end)
+end
+
+function HelpPanel:apply_cmd()
+  local row, _ = unpack(vim.api.nvim_win_get_cursor(0))
+  local mapping = self.maps[row-2]
+  local last_winid = vim.fn.win_getid(vim.fn.winnr("#"))
+
+  if mapping then
+    api.nvim_win_call(last_winid, function()
+      api.nvim_feedkeys(utils.t(mapping[2]), "m", false)
+    end)
+
+    pcall(self.close, self)
+  end
+end
+
+function HelpPanel:init_buffer()
+  HelpPanel:super().init_buffer(self)
+  local conf = get_user_config().keymaps
+  local default_opt = { silent = true, nowait = true, buffer = self.bufid }
+
+  for _, mapping in ipairs(conf.help_panel) do
+    local map_opt = vim.tbl_extend("force", default_opt, mapping[4] or {}, { buffer = self.bufid })
+    vim.keymap.set(mapping[1], mapping[2], mapping[3], map_opt)
+  end
+
+  vim.keymap.set("n", "<cr>", function()
+    self:apply_cmd()
+  end, default_opt)
+end
+
+function HelpPanel:update_components()
+  local keymaps = get_user_config().keymaps
+  local maps = keymaps[self.keymap_name]
+
+  if not maps then
+    utils.err(("Unknown keymap group '%s'!"):format(self.keymap_name))
+  else
+    maps = vim.tbl_map(function(v)
+      local desc = v[4] and v[4].desc
+
+      if not desc then
+        if type(v[3]) == "string" then
+          desc = v[3]
+        elseif type(v[3]) == "function" then
+          local info = debug.getinfo(v[3], "S")
+          desc = ("<Lua @ %s:%d>"):format(info.short_src, info.linedefined)
+        end
+      end
+
+      return utils.vec_join(v, desc)
+    end, maps)
+    -- Sort mappings by description
+    table.sort(maps, function(a, b)
+      a, b = a[5], b[5]
+      -- Ensure lua functions are sorted last
+      if a:match("^<Lua") then a = "~" .. a end
+      if b:match("^<Lua") then b = "~" .. b end
+      return a < b
+    end)
+
+    local lines = { "" }
+    local max_width = 0
+
+    for _, mapping in ipairs(maps) do
+      local txt = string.format("%14s -> %s", mapping[2], mapping[5])
+
+      max_width = math.max(max_width, #txt)
+      table.insert(lines, txt)
+    end
+
+    local height = #lines + 1
+    local width = max_width + 2
+    local title_line = ("Keymaps for '%s' — <cr> to use"):format(self.keymap_name)
+    title_line = string.rep(" ", math.floor(width * 0.5 - #title_line * 0.5) - 1) .. title_line
+    table.insert(lines, 1, title_line)
+
+    self.maps = maps
+    self.lines = lines
+
+    self.config_producer = function()
+      local c = vim.deepcopy(Panel.default_config_float)
+      local viewport_width = vim.o.columns
+      local viewport_height = vim.o.lines
+      c.col = math.floor(viewport_width * 0.5 - width * 0.5)
+      c.row = math.floor(viewport_height * 0.5 - height * 0.5)
+      c.width = width
+      c.height = height
+
+      return c
+    end
+  end
+end
+
+function HelpPanel:render()
+  self.render_data:clear()
+  self.render_data.lines = utils.vec_slice(self.lines or {})
+end
+
+M.HelpPanel = HelpPanel
+return M