doc: document --recurse-submodules for reset and restore

Also unify the formulation about --no-recurse-submodules for checkout
and switch, which we reuse for restore.

And correct the formulation about submodules' HEAD in read-tree, which
we reuse in reset.

Signed-off-by: Damien Robert <damien.olivier.robert+git@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/Documentation/git-reset.txt b/Documentation/git-reset.txt
index 932080c..252e2d4 100644
--- a/Documentation/git-reset.txt
+++ b/Documentation/git-reset.txt
@@ -87,6 +87,12 @@
 	different between `<commit>` and `HEAD`.
 	If a file that is different between `<commit>` and `HEAD` has local
 	changes, reset is aborted.
+
+--[no-]recurse-submodules::
+	When the working tree is updated, using --recurse-submodules will
+	also recursively reset the working tree of all active submodules
+	according to the commit recorded in the superproject, also setting
+	the submodules' HEAD to be detached at that commit.
 --
 
 See "Reset, restore and revert" in linkgit:git[1] for the differences