Patch for https://github.com/mopp/vim/tree/add_flatten

fix_flatten.patch

diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index 22a4c0054..abb9ccfbd 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -4043,10 +4043,10 @@ flatten({list} [, {maxdepth}])					*flatten()*
 			:echo flatten([1, [2], 3])
 <			[1, 2, 3] >
 			:echo flatten([[[1], [2], [3]]], 1)
-
-<			 [[1], [2], [3]]
+<			[[1], [2], [3]]
 							        *E964*
 		{maxdepth} must be positive number.
+
 float2nr({expr})					*float2nr()*
 		Convert {expr} to a Number by omitting the part after the
 		decimal point.
diff --git a/runtime/doc/usr_41.txt b/runtime/doc/usr_41.txt
index c7e595586..6b51e7ba3 100644
--- a/runtime/doc/usr_41.txt
+++ b/runtime/doc/usr_41.txt
@@ -639,6 +639,7 @@ List manipulation:					*list-functions*
 	min()			minimum value in a List
 	count()			count number of times a value appears in a List
 	repeat()		repeat a List multiple times
+	flatten()		Flatten a List
 
 Dictionary manipulation:				*dict-functions*
 	get()			get an entry without an error for a wrong key
diff --git a/src/evalfunc.c b/src/evalfunc.c
index c8c5a41a5..7537891c2 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -3858,9 +3858,7 @@ f_flatten(typval_T *argvars, typval_T *rettv)
     }
 
     if (argvars[1].v_type == VAR_UNKNOWN)
-    {
 	maxdepth = 1;
-    }
     else
     {
 	maxdepth = (long)get_tv_number_chk(&argvars[1], &error);
@@ -3873,8 +3871,8 @@ f_flatten(typval_T *argvars, typval_T *rettv)
 	}
     }
 
-    if ((l = argvars[0].vval.v_list) != NULL
-	    && !tv_check_lock(l->lv_lock, (char_u *)N_("flatten() argument"), TRUE)
+    if ((l = argvars[0].vval.v_list) != NULL && !tv_check_lock(l->lv_lock,
+		(char_u *)N_("flatten() argument"), TRUE)
 	    && list_flatten(l, maxdepth) == OK)
 	copy_tv(&argvars[0], rettv);
 }