Keymapping to search string pattern in LSP workspace

Neovim
2

Following works for me:

vim.keymap.set('n','<leader>f', function()
  local pattern = vim.fn.input("Search pattern: ")
  local cmd = [[vimgrep /]].. pattern .. [[/j `git ls-files --full-name :/ \| sed "s;^;$(git rev-parse --show-toplevel)/;"` | copen]]
  return vim.cmd(cmd)
end,opts)

EDIT: Ensured absolute path file patterns, so that vimgrep has no issues when cwd is somewhere inside the project.
EDIT 2: The only requirement for this method is an initialized Git repository. It doesn’t need Language Server Protocol features. .gitignore will be respected.