Fix some leftover issues with auto-resetting

There doesn't seem to be a way to close the other buffer as well -- ends
up in a segfault. For now, it's best to just reset the buffer and make
saving it safe.

autoload/linediff/differ.vim

@@ -16,6 +16,7 @@ function! linediff#differ#New(sign_name, sign_number)
         \ 'Init':                      function('linediff#differ#Init'),
         \ 'IsBlank':                   function('linediff#differ#IsBlank'),
         \ 'Reset':                     function('linediff#differ#Reset'),
+        \ 'CloseAndReset':             function('linediff#differ#CloseAndReset'),
         \ 'Lines':                     function('linediff#differ#Lines'),
         \ 'Indent':                    function('linediff#differ#Indent'),
         \ 'CreateDiffBuffer':          function('linediff#differ#CreateDiffBuffer'),
@@ -65,6 +66,13 @@ function! linediff#differ#Reset() dict
   let self.is_blank = 1
 endfunction
 
+" Closes the diff buffer and resets. The two actions are separate to avoid
+" problems with closing already closed buffers.
+function! linediff#differ#CloseAndReset() dict
+  call self.CloseDiffBuffer()
+  call self.Reset()
+endfunction
+
 " Extracts the relevant lines from the original buffer and returns them as a
 " list.
 function! linediff#differ#Lines() dict
@@ -134,17 +142,22 @@ endfunction
 " update the other differ's data, provided a few conditions are met. See
 " linediff#differ#PossiblyUpdateOtherDiffer() for details.
 function! linediff#differ#UpdateOriginalBuffer() dict
+  if self.IsBlank()
+    return
+  endif
+
+  let saved_diff_buffer_view = winsaveview()
   let new_lines = getbufline('%', 0, '$')
 
   " Switch to the original buffer, delete the relevant lines, add the new
   " ones, switch back to the diff buffer.
   set bufhidden=hide
   call linediff#util#SwitchBuffer(self.original_buffer)
-  let saved_view = winsaveview()
+  let saved_original_buffer_view = winsaveview()
   call cursor(self.from, 1)
   exe "normal! ".(self.to - self.from + 1)."dd"
   call append(self.from - 1, new_lines)
-  call winrestview(saved_view)
+  call winrestview(saved_original_buffer_view)
   call linediff#util#SwitchBuffer(self.diff_buffer)
   set bufhidden=wipe
 
@@ -158,6 +171,7 @@ function! linediff#differ#UpdateOriginalBuffer() dict
   call self.SetupSigns()
 
   call self.PossiblyUpdateOtherDiffer(new_line_count - line_count)
+  call winrestview(saved_diff_buffer_view)
 endfunction
 
 " If the other differ originates from the same buffer and it's located below

plugin/linediff.vim

@@ -37,19 +37,16 @@ endfunction
 
 command! LinediffReset call s:LinediffReset()
 function! s:LinediffReset()
-  call s:differ_one.CloseDiffBuffer()
-  call s:differ_one.Reset()
-
-  call s:differ_two.CloseDiffBuffer()
-  call s:differ_two.Reset()
+  call s:differ_one.CloseAndReset()
+  call s:differ_two.CloseAndReset()
 endfunction
 
 function! s:PerformDiff()
   call s:differ_one.CreateDiffBuffer("tabedit")
-  autocmd BufUnload <buffer> silent call s:differ_one.Reset()
+  autocmd BufUnload <buffer> silent call s:differ_one.Reset() | silent call s:differ_two.Reset()
 
   call s:differ_two.CreateDiffBuffer("rightbelow vsplit")
-  autocmd BufUnload <buffer> silent call s:differ_two.Reset()
+  autocmd BufUnload <buffer> silent call s:differ_two.Reset() | silent call s:differ_one.Reset()
 
   wincmd t " move to the first diff buffer