do workaround on replacing entire buffer not to move the cursor on un…

…do (issue #8)

Replace current buffer with workaround not to move
the cursor on undo (issue #8)

The points are:
  - Do not touch the first line.
  - Use :put (p, P and :put! is not available).

To meet above condition:
  - Delete all lines except for the first line.
  - Put formatted text except for the first line.

autoload/clang_format.vim

@@ -165,8 +165,34 @@ function! clang_format#replace(line1, line2)
  let formatted = clang_format#format(a:line1, a:line2)
 
  if s:success(formatted)
- call setreg('g', formatted, 'v')
- silent keepjumps normal! ggVG"gp
+ try
+ " Note:
+ " Replace current buffer with workaround not to move
+ " the cursor on undo (issue #8)
+ "
+ " The points are:
+ " - Do not touch the first line.
+ " - Use :put (p, P and :put! is not available).
+ "
+ " To meet above condition:
+ " - Delete all lines except for the first line.
+ " - Put formatted text except for the first line.
+ "
+ let i = stridx(formatted, "\n")
+ if i == -1 || getline(1) !=# formatted[:i-1]
+ throw "fallback"
+ endif
+
+ call setreg('g', formatted[i+1:], 'V')
+ undojoin | normal! 2gg"_dG
+ put g
+ catch
+ " Fallback:
+ " The previous way. It lets the cursor move to the first line
+ " on undo.
+ call setreg('g', formatted, 'V')
+ normal! ggVG"gp
+ endtry
  else
  call s:error_message(formatted)
  endif