Merge pull request rhysd#32 from peplin/31-warn-against-textwidth

Warn of incompatibility between formatexpr and textwidth.

Author: rhysd

README.md

@@ -89,7 +89,9 @@ Formatting is executed on `InsertLeave` event.
 - `g:clang_format#auto_formatexpr`
 
 When the value is 1, `formatexpr` option is set by vim-clang-format automatically in C, C++ and ObjC codes.
-Vim's format mappings (e.g. `gq`) get to use `clang-format` to format.
+Vim's format mappings (e.g. `gq`) get to use `clang-format` to format. This
+option is not comptabile with Vim's `textwidth` feature. You must set
+`textwidth` to `0` when the `formatexpr` is set.
 
 ### Vimrc Example
 

doc/clang-format.txt

@@ -189,7 +189,8 @@ g:clang_format#auto_formatexpr		        *g:clang_format#auto_formatexpr*
 
     When the value is 1, 'formatexpr' option is set automatically in |c|, |cpp|
     and |objc| codes.  Vim's format mappings (e.g. |gq|) get to use |clang-format|
-    to format.
+    to format. This option is not comptabile with Vim's `textwidth` feature. You
+    must set `textwidth` to `0` when the `formatexpr` is set.