From fd834e48eed21cc3c3ab66779a2296a16f41cbca Mon Sep 17 00:00:00 2001
From: Andy Stewart <boss@airbladesoftware.com>
Date: Mon, 4 Feb 2019 14:45:58 +0000
Subject: [PATCH] Combine Diff* foreground colours with SignColumn's
 background.

For default sign colours.

It seems the Diff* highlight groups are generally designed for line
highlighting so they have background colours which differ from the main
background colour.  While desirable for line highlights, this isn't what
we want for the signs.
---
 autoload/gitgutter/highlight.vim | 26 +++++++++++++++++++++++---
 1 file changed, 23 insertions(+), 3 deletions(-)

diff --git a/autoload/gitgutter/highlight.vim b/autoload/gitgutter/highlight.vim
index 62746f7..160856f 100644
--- a/autoload/gitgutter/highlight.vim
+++ b/autoload/gitgutter/highlight.vim
@@ -45,14 +45,19 @@ function! gitgutter#highlight#define_highlights() abort
 
   " Highlights used by the signs.
 
+  " When they are invisible.
   execute "highlight GitGutterAddInvisible    guifg=bg guibg=" . guibg . " ctermfg=" . ctermbg . " ctermbg=" . ctermbg
   execute "highlight GitGutterChangeInvisible guifg=bg guibg=" . guibg . " ctermfg=" . ctermbg . " ctermbg=" . ctermbg
   execute "highlight GitGutterDeleteInvisible guifg=bg guibg=" . guibg . " ctermfg=" . ctermbg . " ctermbg=" . ctermbg
   highlight default link GitGutterChangeDeleteInvisible GitGutterChangeInvisible
 
-  highlight default link GitGutterAdd          DiffAdd
-  highlight default link GitGutterChange       DiffChange
-  highlight default link GitGutterDelete       DiffDelete
+  " When they are visible.
+  " By default use Diff* foreground colors with SignColumn's background.
+  for type in ['Add', 'Change', 'Delete']
+    let [guifg, ctermfg] = s:get_foreground_colors('Diff'.type)
+    execute "highlight GitGutter".type."Default guifg=".guifg." guibg=".guibg." ctermfg=".ctermfg." ctermbg=".ctermbg
+    execute "highlight default link GitGutter".type." GitGutter".type."Default"
+  endfor
   highlight default link GitGutterChangeDelete GitGutterChange
 
   " Highlights used for the whole line.
@@ -126,6 +131,21 @@ function! s:define_sign_line_highlights() abort
   endif
 endfunction
 
+function! s:get_foreground_colors(group) abort
+  redir => highlight
+  silent execute 'silent highlight ' . a:group
+  redir END
+
+  let link_matches = matchlist(highlight, 'links to \(\S\+\)')
+  if len(link_matches) > 0 " follow the link
+    return s:get_foreground_colors(link_matches[1])
+  endif
+
+  let ctermfg = s:match_highlight(highlight, 'ctermfg=\([0-9A-Za-z]\+\)')
+  let guifg   = s:match_highlight(highlight, 'guifg=\([#0-9A-Za-z]\+\)')
+  return [guifg, ctermfg]
+endfunction
+
 function! s:get_background_colors(group) abort
   redir => highlight
   silent execute 'silent highlight ' . a:group