Avoid 2x undo (rhysd#98)

Kind of hard to follow the history of this, but currently (NVIM
v0.5.0-427-g1f56f9a4b) it seems like this undojoin makes some unexpected
behaviour for the user. Unable to tell what-else is unlocked by
removing it, so let's try without it for a while.

Author: Kypert

autoload/clang_format.vim

@@ -236,10 +236,9 @@ function! clang_format#replace(line1, line2, ...) abort
         return
     endif
 
-    let winview = winsaveview()
     let splitted = split(formatted, '\n', 1)
 
-    silent! undojoin
+    let winview = winsaveview()
     if line('$') > len(splitted)
         execute len(splitted) .',$delete' '_'
     endif

test/VimFlavor.lock

@@ -1,3 +1,3 @@
 kana/vim-operator-user (0.1.0)
-kana/vim-vspec (1.6.1)
+kana/vim-vspec (1.9.0)
 rhysd/vim-vspec-matchers (0.0.4)

test/t/clang_format_spec.vim

@@ -457,9 +457,28 @@ describe 'undo formatting text'
         bdelete!
     end
 
+    it 'can make a change, format (constitutes as a second change), then undo and keep the first change'
+        normal! ggOmega
+        ClangFormat
+        " When running :ClangFormat from a normal vim instance, setline() does add an entry in the undolist
+        " For some reason it does not do so when running in this test framework
+        " Also, seems like it is hard to even add another item to the change list too, always rendering:
+        " # number changes  when               saved
+        " #      9       1  0 seconds ago
+        normal! ggOadditional
+        :Debug GetBuffer()
+        " TODO: should enable this
+        " normal! u
+        Expect 0 != search('mega', 'cw')
+        undo
+        Expect 0 == search('mega', 'cw')
+    end
+
     it 'restores previous text as editing buffer normally'
         let prev = GetBuffer()
         ClangFormat
+        let buf = GetBuffer()
+        Expect prev != buf
         undo
         let buf = GetBuffer()
         Expect prev ==# buf