add options variable to isort

autoload/ale/fixers/isort.vim

@@ -5,6 +5,8 @@ call ale#Set('python_isort_executable', 'isort')
 call ale#Set('python_isort_use_global', get(g:, 'ale_use_global_executables', 0))
 
 function! ale#fixers#isort#Fix(buffer) abort
+    let l:options = ale#Var(a:buffer, 'python_isort_options')
+
     let l:executable = ale#python#FindExecutable(
     \   a:buffer,
     \   'python_isort',
@@ -17,6 +19,6 @@ function! ale#fixers#isort#Fix(buffer) abort
 
     return {
     \   'command': ale#path#BufferCdString(a:buffer)
-    \   .   ale#Escape(l:executable) . ' -',
+    \   .   ale#Escape(l:executable) . ' ' . l:options . ' -',
     \}
 endfunction

doc/ale-python.txt

@@ -145,6 +145,14 @@ g:ale_python_isort_executable                   *g:ale_python_isort_executable*
   See |ale-integrations-local-executables|
 
 
+g:ale_python_isort_options                      *g:ale_python_isort_options*
+                                                *b:ale_python_isort_options*
+  Type: |String|
+  Default: `''`
+
+  This variable can be set to pass extra options to isort.
+
+
 g:ale_python_isort_use_global                   *g:ale_python_isort_use_global*
                                                 *b:ale_python_isort_use_global*
   Type: |Number|