Merge branch 'pb/do-not-recurse-grep-no-index'

"git grep --no-index" should not get affected by the contents of
the .gitmodules file but when "--recurse-submodules" is given or
the "submodule.recurse" variable is set, it did.  Now these
settings are ignored in the "--no-index" mode.

* pb/do-not-recurse-grep-no-index:
  grep: ignore --recurse-submodules if --no-index is given

Documentation/git-grep.txt

@@ -96,7 +96,8 @@ OPTIONS
 	Recursively search in each submodule that has been initialized and
 	checked out in the repository.  When used in combination with the
 	<tree> option the prefix of all submodule output will be the name of
-	the parent project's <tree> object.
+	the parent project's <tree> object. This option has no effect
+	if `--no-index` is given.
 
 -a::
 --text::