Revert to non-binary writefile() for writing buffer.

The previous commit switched use of writefile() to binary mode so that
we could prevent a newline being added to a completely empty buffer.
Evidently, however, binary mode has side effects (see #567) so this
commit returns to non-binary mode - with a simpler fix for completely
empty files.

Unfortunately this implementation does not work for noeol files - see
the failing test - because writefile() does not take account of
'nofixeol' (unlike :write).  This is suboptimal but acceptable because
noeol files are not be encountered often.

See #567.

autoload/gitgutter/diff.vim

@@ -375,14 +375,10 @@ function! s:write_buffer(bufnr, file)
   let bufcontents = getbufline(a:bufnr, 1, '$')
 
   if bufcontents == [''] && line2byte(1) == -1
-    " Special case: empty buffer; do not write an empty line in this case.
+    " Special case: completely empty buffer.
     " A nearly empty buffer of only a newline has line2byte(1) == 1.
-  else
-    if getbufvar(a:bufnr, '&endofline')
-          \ || (!getbufvar(a:bufnr, '&binary')
-          \     && (!exists('+fixendofline') || getbufvar(a:bufnr, '&fixendofline')))
-      call add(bufcontents, '')
-    endif
+    call writefile([], a:file)
+    return
   endif
 
   if getbufvar(a:bufnr, '&fileformat') ==# 'dos'
@@ -398,7 +394,7 @@ function! s:write_buffer(bufnr, file)
     let bufcontents[0]=''.bufcontents[0]
   endif
 
-  call writefile(bufcontents, a:file, 'b')
+  call writefile(bufcontents, a:file)
 endfunction
 
 

test/test_gitgutter.vim

@@ -669,7 +669,7 @@ function Test_empty_file()
 
   " 1 line file without newline
   " Vim will force a newline unless we tell it not to.
-  call system('echo -n "a" > oneline.txt && git add oneline.txt')
+  call system('echo -n a > oneline.txt && git add oneline.txt')
   set noeol nofixeol
   edit! oneline.txt