AI generated commit messages

[aweis89]

My new git setup for committing (and pushing) changes with AI generated messages. It uses fugitive to execute the git commands and autocommands to update the COMMIT_EDITMSG used by git commit -v (which also shows diffs bellow the commit message). It works when running git commit -v from the command line as well, as long as nvim is setup as the git editor.

lua/plugins/git.lua:

return {
  {
    "tpope/vim-fugitive",
    cmd = { "Git" },
    keys = {
      -- see autocmds.lua for AI auto-generated functionality
      { "<leader>gc", "<cmd>tab Git commit -v<cr>", desc = "Git commit" },
    },
  },
}

lua/config/autocmds.lua:

local function augroup(name)
  return vim.api.nvim_create_augroup("lazyvim_" .. name, { clear = true })
end

-- Autocommand to populate commit message using ai-commit-msg script
vim.api.nvim_create_autocmd("BufWinEnter", {
  group = augroup("ai_commit_msg_populate"), -- Renamed group for clarity
  pattern = "COMMIT_EDITMSG",
  callback = function()
    vim.system({ "ai-commit-msg" }, {}, function(res)
      vim.schedule(function()
        if res.code ~= 0 then
          vim.notify(res.stderr)
          return
        end
        local msg = res.stdout
        if msg == nil or msg == "" then
          vim.notify("No commit message")
        else
          vim.api.nvim_buf_set_lines(0, 0, 1, false, vim.split(msg, "\n"))
        end
      end)
    end)
  end,
})

-- Autocommand to prompt for push after writing commit message
vim.api.nvim_create_autocmd("BufWritePost", {
  group = augroup("ai_commit_push_prompt"),
  pattern = "COMMIT_EDITMSG",
  callback = function(args)
    -- Defer the prompt slightly to allow git commit process to potentially start/finish
    vim.defer_fn(function()
      -- Get the current branch name
      local branch_name = vim.fn.trim(vim.fn.system("git rev-parse --abbrev-ref HEAD"))
      -- Ask the user if they want to push
      local prompt_message = string.format("Push commit to '%s'? (y/N): ", branch_name)
      vim.ui.input({ prompt = prompt_message }, function(input)
        if input and input:lower() == "y" then
          vim.cmd("Git push")
        end
      end)
    end, 100) -- Small delay (100ms)
  end,
})

The ai-commit-msg script that uses aichat to generate the commit message (needs to be in path of course).
.local/bin/ai-commit-msg:

#!/bin/bash
git diff --staged | aichat \
  --model gemini:gemini-2.0-flash \
  "Respond with a conventional git commit message for these changes. Don't add any extra text aside from the commit message."

To trigger, after staging commits, run :tab Git commit -v or <leader>gc> or git commit -v from the command line

Bonus: trigger the workflow directly from the Snacks git_status picker after doing the file staging there:

picker = {
  actions = {
    ["commit"] = function(picker)
      picker:close()
      -- see autocmds.lua for AI auto-generated functionality
      vim.cmd("tab Git commit -v")
    end,
  },
  sources = {
    git_status = {
      win = {
        input = {
          keys = {
            ["<localleader>g"] = { "commit", mode = { "n", "i" } },
          }
        }
      }
    }
  }
}