Added a `vim-gutentags` extension

Added a segment that displays whether gutentags is running a ctags
instance.

autoload/airline/extensions.vim

@@ -307,6 +307,11 @@ function! airline#extensions#load()
     call add(loaded_ext, 'capslock')
   endif
 
+  if (get(g:, 'airline#extensions#gutentags#enabled', 1) && get(g:, 'loaded_gutentags', 0))
+    call airline#extensions#gutentags#init(s:ext)
+    call add(loaded_ext, 'gutentags')
+  endif
+
   if (get(g:, 'airline#extensions#xkblayout#enabled', 1) && exists('g:XkbSwitchLib'))
     call airline#extensions#xkblayout#init(s:ext)
     call add(loaded_ext, 'xkblayout')

autoload/airline/extensions/gutentags.vim

@@ -0,0 +1,16 @@
+" MIT License. Copyright (c) 2014-2018 Mathias Andersson et al.
+" vim: et ts=2 sts=2 sw=2
+
+scriptencoding utf-8
+
+if !get(g:, 'loaded_gutentags', 0)
+  finish
+endif
+
+function! airline#extensions#gutentags#status()
+  return gutentags#statusline() =~# '^TAGS' ? 'Gen. tags' : ''
+endfunction
+
+function! airline#extensions#gutentags#init(ext)
+  call airline#parts#define_function('gutentags', 'airline#extensions#gutentags#status')
+endfunction

autoload/airline/init.vim

@@ -149,6 +149,7 @@ function! airline#init#bootstrap()
         \ 'ycm_error_count', 'ycm_warning_count', 'neomake_error_count',
         \ 'neomake_warning_count', 'ale_error_count', 'ale_warning_count'])
   call airline#parts#define_text('capslock', '')
+  call airline#parts#define_text('gutentags', '')
   call airline#parts#define_text('xkblayout', '')
   call airline#parts#define_text('keymap', '')
 
@@ -180,7 +181,7 @@ function! airline#init#sections()
     let g:airline_section_gutter = airline#section#create(['%='])
   endif
   if !exists('g:airline_section_x')
-    let g:airline_section_x = airline#section#create_right(['tagbar', 'filetype'])
+    let g:airline_section_x = airline#section#create_right(['tagbar', 'gutentags', 'filetype'])
   endif
   if !exists('g:airline_section_y')
     let g:airline_section_y = airline#section#create_right(['ffenc'])

doc/airline.txt

@@ -885,6 +885,12 @@ NrrwRgn <https://github.com/chrisbra/NrrwRgn>
 * enable/disable NrrwRgn integration >
   let g:airline#extensions#nrrwrgn#enabled = 1
 
+-------------------------------------                     *airline-gutentags*
+vim-gutentags <https://github.com/ludovicchabant/vim-gutentags>
+
+* enable/disable vim-gutentags integration >
+  let g:airline#extensions#gutentags#enabled = 1
+
 -------------------------------------                     *airline-capslock*
 vim-capslock <https://github.com/tpope/vim-capslock>
 

t/init.vim

@@ -34,7 +34,7 @@ describe 'init sections'
   end
 
   it 'section x should be filetype'
-    Expect g:airline_section_x == '%{airline#util#wrap(airline#parts#filetype(),0)}'
+    Expect g:airline_section_x == '%{airline#util#prepend(\"\",0)}%{airline#util#wrap(airline#parts#filetype(),0)}'
   end
 
   it 'section y should be fenc and ff'