feat: add diagnostic troubleshooting command

lua/CopilotChat/init.lua

@@ -33,6 +33,23 @@ M.setup = function(options)
     end, { nargs = '*', range = true })
   end
 
+  -- Troubleshoot and fix the diagnostic issue at the current cursor position.
+  utils.create_cmd('CopilotChatFixDiagnostic', function()
+    local diagnostic = utils.get_diagnostics()
+    local file_name = vim.fn.expand('%:t')
+    local line_number = vim.fn.line('.')
+    -- Copy all the lines from current buffer to unnamed register
+    vim.cmd('normal! ggVG"*y')
+    vim.cmd(
+      'CopilotChat Please assist with the following diagnostic issue in file: "'
+        .. file_name
+        .. ':'
+        .. line_number
+        .. '". '
+        .. diagnostic
+    )
+  end, { nargs = '*', range = true })
+
   -- Show debug info
   utils.create_cmd('CopilotChatDebugInfo', function()
     -- Get the log file path

lua/CopilotChat/utils.lua

@@ -52,4 +52,26 @@ M.log_error = function(...)
   log.error(...)
 end
 
+--- Get diagnostics for the current line
+--- It uses the built-in LSP client in Neovim to get the diagnostics.
+--- @return string
+M.get_diagnostics = function()
+  local buffer_number = vim.api.nvim_get_current_buf()
+  local cursor = vim.api.nvim_win_get_cursor(0)
+  local line_diagnostics = vim.lsp.diagnostic.get_line_diagnostics(buffer_number, cursor[1] - 1)
+
+  if #line_diagnostics == 0 then
+    return 'No diagnostics available'
+  end
+
+  local diagnostics = {}
+  for _, diagnostic in ipairs(line_diagnostics) do
+    table.insert(diagnostics, diagnostic.message)
+  end
+
+  local result = table.concat(diagnostics, '. ')
+  result = result:gsub('^%s*(.-)%s*$', '%1'):gsub('\n', ' ')
+  return result
+end
+
 return M