Declare both git-switch and git-restore experimental

These two commands are basically redesigned git-checkout. We will not
have that many opportunities to redo (because we run out of verbs, and
that would also increase maintenance cost).

To play it safe, let's declare the two commands experimental in one or
two releases. If there is a serious flaw in the UI, we could still fix
it. If everything goes well and nobody complains loudly, we can remove
the experimental status by reverting this patch.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-restore.txt

@@ -28,6 +28,8 @@ commit as the restore source.
 See "Reset, restore and revert" in linkgit:git[1] for the differences
 between the three commands.
 
+THIS COMMAND IS EXPERIMENTAL. THE BEHAVIOR MAY CHANGE.
+
 OPTIONS
 -------
 -s <tree>::

Documentation/git-switch.txt

@@ -29,6 +29,8 @@ Switching branches does not require a clean index and working tree
 however if the operation leads to loss of local changes, unless told
 otherwise with `--discard-changes` or `--merge`.
 
+THIS COMMAND IS EXPERIMENTAL. THE BEHAVIOR MAY CHANGE.
+
 OPTIONS
 -------
 <branch>::