From 64b0fabd853d0e838bddb9645e92d41413e63e61 Mon Sep 17 00:00:00 2001
From: Tom Ryder <tom@sanctum.geek.nz>
Date: Sun, 23 Jun 2019 23:06:08 +1200
Subject: Replace existing Markdown heading underlines

---
 vim/autoload/markdown.vim | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/vim/autoload/markdown.vim b/vim/autoload/markdown.vim
index c0818246..8bac8045 100644
--- a/vim/autoload/markdown.vim
+++ b/vim/autoload/markdown.vim
@@ -11,8 +11,13 @@ function! markdown#Heading(char) abort
   " heading text
   let underline = repeat(a:char, strlen(heading))
 
-  " Append the heading text to the buffer on a new line after the heading
-  call append(pos[1], underline)
+  " If the line after this one looks like it's already an underline, replace
+  " it; otherwise, create a new underline
+  if getline(pos[1] + 1) =~# '^[-=]\{2,}$'
+    call setline(pos[1] + 1, underline)
+  else
+    call append(pos[1], underline)
+  endif
 
   " Move to the first column of the underline we just inserted
   let pos[1] += 1
-- 
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