refactor(gitcommit): improve type annotations and remove redundant filetype check

- add specific type annotations for Buffer configuration
- remove unnecessary filetype check in keymap setup
- simplify Buffer.setup call with optional parameter
- add CodeCompanion.GitCommit.ExtensionOpts.Buffer type definition

Author: jinzhongjia

lua/codecompanion/_extensions/gitcommit/buffer.lua

@@ -4,7 +4,7 @@ local Buffer = {}
 local Git = require("codecompanion._extensions.gitcommit.git")
 local Generator = require("codecompanion._extensions.gitcommit.generator")
 
----@type table Default configuration
+---@type CodeCompanion.GitCommit.ExtensionOpts.Buffer Default configuration
 local default_config = {
   enabled = true,
   keymap = "<leader>gc",
@@ -14,7 +14,7 @@ local default_config = {
 local config = {}
 
 ---Setup buffer keymaps for gitcommit filetype
----@param opts table Configuration options
+---@param opts? CodeCompanion.GitCommit.ExtensionOpts.Buffer Configuration options
 function Buffer.setup(opts)
   config = vim.tbl_deep_extend("force", default_config, opts or {})
 
@@ -40,11 +40,6 @@ function Buffer._setup_gitcommit_keymap(bufnr)
     return
   end
 
-  local ft = vim.api.nvim_get_option_value("filetype", { buf = bufnr })
-  if ft ~= "gitcommit" then
-    return
-  end
-
   -- Set buffer-local keymap
   vim.keymap.set("n", config.keymap, function()
     Buffer._generate_and_insert_commit_message(bufnr)

lua/codecompanion/_extensions/gitcommit/init.lua

@@ -49,7 +49,7 @@ return {
       Buffer.setup(opts.buffer)
     else
       -- Enable buffer keymaps by default
-      Buffer.setup({})
+      Buffer.setup()
     end
 
     -- Create user commands for git commit generation

lua/codecompanion/_extensions/gitcommit/types.lua

@@ -4,8 +4,13 @@
 ---@field setup fun(opts: CodeCompanion.GitCommit.ExtensionOpts): nil
 ---@field exports CodeCompanion.GitCommit.Exports
 
+---@class CodeCompanion.GitCommit.ExtensionOpts.Buffer
+---@field enabled boolean Enable buffer-specific keymap for git commit
+---@field keymap string Keymap for generating commit message in git commit buffer
+
 ---@class CodeCompanion.GitCommit.ExtensionOpts
 ---@field add_slash_command? boolean Add /gitcommit slash command to chat buffer
+---@field buffer? CodeCompanion.GitCommit.ExtensionOpts.Buffer Enable buffer-specific keymap for git commit
 
 ---@class CodeCompanion.GitCommit.Exports
 ---@field generate fun(callback: fun(result: string|nil, error: string|nil)): nil