Add g:tagbar_highlight_follow_insert option (#725)

This adds an option making the highlight in the Tagbar follow the cursor
in insert mode as well. This feature is guarded behind an option because
it may introduce some delay in the input.

GitHub: closes #724

autoload/tagbar.vim

@@ -576,6 +576,10 @@ function! s:CreateAutocommands() abort
         " was changed by an external command; see commit 17d199f
         autocmd BufReadPost,BufEnter,CursorHold,FileType * call
                     \ s:AutoUpdate(fnamemodify(expand('<afile>'), ':p'), 0)
+        if g:tagbar_highlight_follow_insert
+            autocmd CursorHoldI * call
+                        \ s:AutoUpdate(fnamemodify(expand('<afile>'), ':p'), 0)
+        endif
         autocmd BufDelete,BufWipeout *
                     \ nested call s:HandleBufDelete(expand('<afile>'), expand('<abuf>'))
 

doc/tagbar.txt

@@ -1094,6 +1094,19 @@ containing the tag without scrolling the window.  If the tag is not visible
 in the window then the window will be scrolled and the tag (and cursor)
 placed in the location dictated by |g:tagbar_jump_offset|.
 
+                                           *g:tagbar_highlight_follow_insert*
+g:tagbar_highlight_follow_insert~
+Default: 0
+
+If set to non-zero, the highlight of the current tag in the Tagbar will follow
+the cursor in insert mode as well, after a short pause once the cursor stops
+moving. Enabling this option may introduce some lag during the input, so it is
+disabled by default.
+
+Example:
+>
+        let g:tagbar_highlight_follow_insert = 1
+<
                                                   *g:tagbar_highlight_method*
 g:tagbar_highlight_method~
 Default: 'nearest-stl'

plugin/tagbar.vim

@@ -100,6 +100,7 @@ function! s:setup_options() abort
         \ ['jump_lazy_scroll', 0],
         \ ['left', 0],
         \ ['help_visibility', 0],
+        \ ['highlight_follow_insert', 0],
         \ ['highlight_method', 'nearest-stl'],
         \ ['ignore_anonymous', 0],
         \ ['position', default_pos],