Fix invalid range in SetexToAtx

Author: lggruspe

ftplugin/markdown.vim

@@ -494,7 +494,9 @@ endfunction
 function! s:SetexToAtx(line1, line2)
     let l:originalNumLines = line('$')
     execute 'silent! ' . a:line1 . ',' . a:line2 . 'substitute/\v(.*\S.*)\n\=+$/# \1/'
-    execute 'silent! ' . a:line1 . ',' . a:line2 . 'substitute/\v(.*\S.*)\n-+$/## \1/'
+
+    let l:changed = l:originalNumLines - line('$')
+    execute 'silent! ' . a:line1 . ',' . (a:line2 - l:changed) . 'substitute/\v(.*\S.*)\n-+$/## \1'
     return l:originalNumLines - line('$')
 endfunction
 

test/setextoatx.vader

@@ -20,3 +20,29 @@ Expect (convert setex-style headings to atx):
   ## b
 
   ## b
+
+Given markdown;
+a
+=
+
+b
+=
+
+c
+-
+
+d
+-
+
+Execute (SetexToAtx with range):
+  :1,8SetexToAtx
+
+Expect (only convert setex headings in original range):
+  # a
+
+  # b
+
+  ## c
+
+  d
+  -