new fixer elixir mix format

(only available in elixir > 1.6)

autoload/ale/fixers/mix_format.vim

@@ -0,0 +1,17 @@
+" Author: carakan <carakan@gmail.com>
+" Description: Fixing files with elixir formatter 'mix format'.
+
+call ale#Set('elixir_mix_executable', 'mix')
+
+function! ale#fixers#mix_format#GetExecutable(buffer) abort
+    return ale#Var(a:buffer, 'elixir_mix_executable')
+endfunction
+
+function! ale#fixers#mix_format#Fix(buffer) abort
+    return {
+    \   'command': ale#handlers#elixir#GetExecutable(a:buffer)
+    \       . ale#fixers#mix_format#GetExecutable(a:buffer)
+    \       . ' format %t',
+    \   'read_temporary_file': 1,
+    \}
+endfunction