vimrc: Wrap FugitiveHead() output

vimrc

@@ -189,6 +189,10 @@ nmap <leader>gg :Rg<cr>
 
 " Lightline configuration:
 packadd! lightline.vim
+function! GitHead()
+  return '[' . FugitiveHead() . ']'
+endfunction
+
 set laststatus=2
 let g:lightline = {
       \ 'colorscheme': 'seoul256',
@@ -200,7 +204,7 @@ let g:lightline = {
       \ },
       \ 'component_function': {
       \   'gobuild': 'go#statusline#Show',
-      \   'gitbranch': 'FugitiveHead',
+      \   'gitbranch': 'GitHead',
       \ },
       \ 'mode_map': {
       \   'n' : 'N',