can choice to use gina's extension

fix typo

add v:version >= 800and remove v:version > 704

fix CI error

autoload/airline/extensions.vim

@@ -34,7 +34,7 @@ let s:filetype_overrides = {
       \ 'vimshell': ['vimshell','%{vimshell#get_status_string()}'],
       \ }
 
-if exists(':Gina') && (v:version > 704 || (v:version == 704 && has("patch1898")))
+if airline#util#has_gina() && get(g:, 'airline#extensions#gina_status', 1)
   " Gina needs the Vim 7.4.1898, which introduce the <mods> flag for custom commands
   let s:filetype_overrides['gina-status'] = ['gina', '%{gina#component#repo#preset()}' ]
   let s:filetype_overrides['diff'] = ['gina', '%{gina#component#repo#preset()}' ]

autoload/airline/util.vim

@@ -137,7 +137,7 @@ endfunction
 
 function! airline#util#has_gina()
   if !exists("s:has_gina")
-    let s:has_gina = exists(':Gina')
+    let s:has_gina = (exists(':Gina') && v:version >= 800)
   endif
   return s:has_gina
 endfunction

doc/airline.txt

@@ -709,6 +709,10 @@ gina.vim <https://github.com/lambdalisue/gina.vim>
 Airline displays the gina.vim specific statusline.
 (for details, see the help of gina.vim)
 
+* enable/disable bufferline integration >
+  let g:airline#extensions#gina_status = 1
+<  default: 1
+
 -------------------------------------                     *airline-grepper*
 vim-grepper <https://github.com/mhinz/vim-grepper>