Add clang-format fixer for C/C++ (#873)

* Add clang-format fixer for C/C++

* Document clang-format options

* Refer ale-cpp-clangformat to ale-c-clangformat

autoload/ale/fix/registry.vim

@@ -82,6 +82,11 @@ let s:default_registry = {
 \       'suggested_filetypes': ['php'],
 \       'description': 'Fix PHP files with phpcbf.',
 \   },
+\   'clang-format': {
+\       'function': 'ale#fixers#clangformat#Fix',
+\       'suggested_filetypes': ['c', 'cpp'],
+\       'description': 'Fix C/C++ files with clang-format.',
+\   },
 \}
 
 " Reset the function registry to the default entries.

autoload/ale/fixers/clangformat.vim

@@ -0,0 +1,21 @@
+" Author: Peter Renström <renstrom.peter@gmail.com>
+" Description: Fixing C/C++ files with clang-format.
+
+call ale#Set('c_clangformat_executable', 'clang-format')
+call ale#Set('c_clangformat_use_global', 0)
+call ale#Set('c_clangformat_options', '')
+
+function! ale#fixers#clangformat#GetExecutable(buffer) abort
+    return ale#node#FindExecutable(a:buffer, 'c_clangformat', [
+    \   'clang-format',
+    \])
+endfunction
+
+function! ale#fixers#clangformat#Fix(buffer) abort
+    let l:options = ale#Var(a:buffer, 'c_clangformat_options')
+
+    return {
+    \   'command': ale#Escape(ale#fixers#clangformat#GetExecutable(a:buffer))
+    \       . ' ' . l:options,
+    \}
+endfunction